The goal of this post is to outline some of the questionable players going forward, not to create a catalog of every fantasy football player. Players heavily on waivers (under about 70%) won't be featured here. Guys like Drew Brees and Arian Foster won't be found here. If you don't know what to do with them you shouldn't be playing fantasy.
Players will be split by position first and then players will be ranked Seek, meaning they are currently undervalued and are ripe for beneficial trades, Keep, meaning they are right on value and that you won'[t get from a trade what they are worth on your team, Drop, meaning they are just wasting space on your bench right now, and Trade. Trade can come in two different varieties. On the one hand you can trade a player because he has been playing really well and is likely to be more valuable now than at any point in the future. The other possibility is that this player is doing poorly and is valuable only based on name recognition at this point. He is likely to only lose value from this point on.
Keep: Joe Flacco - Joe Flacco has been better than advertised in a revamped Ravens passing attack and he is likely to keep playing well. While Ray Rice might get more carries going forward, Flacco should remain an excellent spot starter or reserve QB. He hasn't played well enough for anyone to actively seek him out and make you a good enough trade offer, so you are best off sitting on him or playing him until someone is in desperate need.
Keep: Cam Newton - Newton is still an elite QB and his owner likely won't part with him for cheap after spending a first to third round pick on him. He might be underachieving, but he is still a great starting QB with huge potential. Don't trade him for anything less than a mid-level RB1 like Darren McFadden or better.
Seek: Matthew Stafford - Stafford has been playing poorly through the first four weeks of the season and now has a bye week to think about it. Most of the Stafford owners are getting tired of his continual failures and you might be able to find a trade partner with a weak RB or WR corps who would be willing to trade him away for a mid-level RB or WR. Don't go in with someone like MJD, but if you can parlay Fred Jackson into Matthew Stafford you're doing your team a huge favor.
Trade/Drop: Philip Rivers - Rivers is on his last leg as a fantasy starter. He hasn't turned around from his terrible 2011 campaign and the weak receiving corps around him doesn't help. If you can find a desperate trade partner willing to give up a decent running back or receiver (don't expect a starter) take the trade. It looks like the waiver wire quarterbacks are going to outscore him most weeks.
Keep: Peyton Manning - Manning is playing about as well as could be anticipated after a full season away from competitive football. He isn't great against good defenses but he is still tearing up the bad ones. I traded away Doug Martin for him last week. He's definitely worth more than that, but you aren't going to garner the high level of player you would need to replace him. Your best bet is to hold on to him for the time being if you're using him.
Trade: Robert Griffin III - RG3 has been treating fantasy owners well, but he's likely fall off pretty quickly going forward. He has never been the passing threat that Cam Newton was in his rookie season, and defenses are going to start picking up on the Shanahan package at some point this season. Right now you can probably get a really strong player to supplement your team, and you likely grabbed a strong quarterback before RG3. You'll get a nice deal right now if you're willing to dangle him out there. Odds are that his value goes down as the season progresses.
Trade: Michael Vick - Vick was made of fine china before the season started and the Eagles offensive line is still weak. Vick is being hit with alarming frequency and it is only a matter of time before he gets injured for good. If you can get a top-level WR or a mid-level RB for him you'll be in good shape going forward. I'd make a trade straight up for Eli Manning if it came along.
Keep: Tony Romo - Romo's trade value won't be any lower unless he reaches the drop-point. Odds are that he moves up throughout the season to be a decent quarterback, and he probably would have had a great fantasy game if Dez Bryant wasn't hell-bent on ruining the Cowboys Monday night. Hold tight unless you can afford to go after him.
Seek: Trent Richardson - If you can find a trade partner willing to part with Trent Richardson you should take it. He is going to start getting serious touches from the Browns and he is good enough to make something happen with those touches. He's going to be a RB1 going forward now that his knee is healthy.
Trade: Michael Turner - Turner had a huge game against the Panthers, but he has been pretty lackluster thusfar this season. He is an older back who can still turn it on when he needs to, but isn't going to make a lot of big plays. He slowed down towards the end of last season and is likely to do the same this season.
Keep: Stevan Ridley - It seems like Ridley is going to continue playing at the level of an RB2, but I don't think you're going to find the trade market very receptive to him. He doesn't have a whole lot of strong name recognition and you would have to part with him for a lot less than he is worth to your team. Hold on to him for now.
Trade: Fred Jackson - Fred Jackson is unlikely to reach the value he had at the beginning of the season, so you should trade him away now if you can. C.J. Spiller proved to be and extremely good running back during his weeks atop the Bills depth chart, and Jackson sustained a much more serious injury. His age means that he is more likely to be injured going forward, so let him go if you can afford to. I traded him away for Steve Smith before the week started even though I wasn't going to play Smith this week.
Keep/Seek: C.J. Spiller - Spiller is the younger, faster back for the Bills and is more likely to become and remain the starter going forward. He was leading the NFL in rushing before sustaining his shoulder injury, and if someone is willing to part with him for cheap you should go for him.
Keep: Mikel LeShoure - At this point there isn't a whole lot to support you going after or trading away LeShoure. He could play an integral role in the Lions offense or he could fade away into obscurity. With the Lions going to bye week you should sit tight on him.
Keep: Chris Johnson - After three weeks of stress from the owners of CJ2k there was finally some progress towards his expected value. It is very unlikely that you'll find a trade partner willing to give you anything close to what you paid for Chris Johnson, and you certainly can't give up his potential for cheap. Hold tight for now and use him as a flex or bye-week filler until we have more data.
Seek: Ryan Mathews - If you can come by Ryan Mathews for cheap then you should make a move. He's an excellent player who had an unfortunate fumble in his first game back. All signs point to him being successful in the future despite the successes of Jackie Battle. He's definitely worth a mid-level WR or QB if you can swing it.
Keep: Jamaal Charles - You aren't going to find anyone willing to give you a huge prize for Jamaal Charles at this point, but he's definitely worth it. Play Charles happily as an RB1.
Drop: Peyton Hillis - He's injured and playing terribly. If anyone is willing to make a trade for him take it. Otherwise there are plenty of waiver acquisitions right now who will do more for you.
Trade: Frank Gore - Gore has been playing well so far, but you can assume that he will start heading downhill as the season progresses. He has been unable to stay healthy over the past few seasons and there is nothing to suggest he won't be injured again this season. If the right prize comes along don't hesitate to trade him.
Keep/Trade: Shonn Greene - The first six weeks of the Jets' season is rough against the run, but it does get better going forward. I don't know what you can get for him at this point, but dropping a starting running back isn't typically smart in most leagues. You are better off holding him and waiting for a good game than dropping him now.
Keep: Steven Jackson - Jackson is valuable but injured. You can't trade him or release him right now, so hold on to him.
Seek: Reggie Bush - There is no reason to avoid Bush if you can find a way to get him. He is much more valuable than someone like Donald Brown, but depending on the owner's depth you might have trouble finding a good price. If you get him you likely won't be disappointed though. He has good potential with the Dolphins.
Keep: Darren McFadden - He hasn't been playing especially well so far, but he still has huge potential. You won't get his worth right now, so just keep a hold on him for now.
Trade/Keep: Willis McGahee - McGahee has a few good games under his belt, but I don't trust him as a top-level RB yet. He is still old and he hasn't played against too many good defenses yet. The injury risk with him is high, so trade him if you get a good offer. Your goal should be to trade him.
Trade: BenJarvus Green-Ellis - He has been a great story so far, but he has gotten less effective as the year as rolled on. With Bernard Scott working his way back the RBBC is going to get rolling. His fumble-proof time is long passed, so see if you can get something of value before he becomes less valuable.
Keep: Alfred Morris - The trade value of Morris is lagging way behind his true value. The best thing you can do is hold on to him until someone comes to you with an offer fitting his value.
Trade: Doug Martin - Martin's value is going to fall precipitously if he doesn't start getting carries. Rookie running backs typically don't have good first seasons, and Martin is no exception of the rule. It doesn't help that the Bucs offense is lackluster, but see if you can get something for him soon.
Seek: DeMarco Murray - If you can get a hold on Murray you should go for it. He should be a low-level RB1 for the rest of the season, but don't break the bank for him. The Cowboys offense is in shambles.
Trade/Drop: Michael Bush - Bush has never been a good back, and he isn't one now. The proof is in the last few games while Forte was injured. Get what you can from him or cut him lose.
**Note: There are a lot of receivers (Dez Bryant, Percy Harvin, Brandon Marshall, Steve Smith, etc. who are below expectations at this time in the year. Keep them. You can't get any kind of return on investment right now and it is way too early to panic about any of them. Top flight receivers are unique and all of these guys can turn it around.)
Keep: Larry Fitzgerald - He would have been a seek before the last two games, but most owners are still going to expect big value for Fitzgerald. He probably isn't worth the value of his name right now.
Seek: Danny Amendola - After one huge game, Amendola cooled off pretty rapidly. I think the general conception about his value is still very low at this point, so if you need a bye-week receiver you should target him.
Trade/Keep: Greg Jennings - Jennings has very little value right now because of his groin injury, but he still has a strong enough name recognition factor to be valuable. If you could trade him away for someone like DeMarco Murray, do it. Otherwise you might just have to sit tight and hope he heals up quickly.
Keep: Jordy Nelson - Nelson has been mediocre to this point in the season, but Aaron Rodgers finally turned on his game in week 4, so Nelson should improve from this point forward.
Keep: Reggie Wayne - Wayne is Andrew Luck's favorite target. He is probably worth a low-level RB1, but you're unlikely to get that for him. If he finds the end zone more often during the rest of the season he could be elite. If you get a good trade, feel free to move him, just as a precaution against his age.
Keep/Trade: Torrey Smith - Smith has two really solid games in a row after two extremely disappointing games. The truth of the matter is that you never really know what you are going to get from him. The trade value probably isn't there right now, since he is a situational starting WR, but if anything consistent comes along you should take it.
Keep: Dwayne Bowe - It's hard to see the Chiefs' defense getting any better, so Bowe should keep blowing up the 4th quarter. He's a top-level receiver right now.
Drop: Greg Little - Little has too many drops and is playing with Weeden. Keep him or drop him. There are more consistent and better options out there.
Keep: Hakeem Nick - Nicks is being a pain in the ass with these nagging injuries. The unfortunate truth is that you aren't going to find a good trade partner at this point in the season for an injured receiver. If something good comes along, go with it.
Keep: Roddy White - White has been playing big-boy football for the last few weeks. He's probably going to cool down but still play like a top-10 receiver for the rest of the season. Unless he is part of a monster deal where you get his true value, keep starting him.
Keep/Trade: Julio Jones - Turns out that Julio isn't exactly what we expected after his monster first game. He's still a good receiver, but if you can get a valuable replacement you might want to make that move. He's not helping your team right now.
Seek: Pierre Garcon - Garcon owners are frustrated with the injuries and lack of production after game one. This is a great time to play some low-ball and try to get him for a guy like Shonn Green or Doug Martin. He probably has that level of value going forward.
Seek: Kenny Britt - Britt is a great receiver who has started off slow. If you can get him onto your bench for cheap you should do it now.
Keep/Trade: Brandon Lloyd - I don't have any idea what Lloyd is going to do from this point forward, but he definitely hasn't lived up to your expectations. The garbage touchdown last week was a nice reward for sticking with him, but I don't know how many more of those you're going to get. If the right trade comes along, take it. Otherwise you'll just have to deal with his current production.
Drop: Robert Meachem - Meachem never lived up to expectations and it largely expendable right now. Keep him if there are no better options on waivers.
Keep: Malcom Floyd - He definitely isn't elite but you won't find a suitable trade partner in most leagues and he is better than the guys on waivers. Just hold on to him as a WR4/5.
Keep: Marques Colston - Before last game he would have been a "seek" player. He has a good track record against the Packers, but don't expect that level of performance every week. He is still hobbled by that foot injury, but he seems to be getting better.
Seek: Andre Johnson - The Texans rarely throw the ball, and why would they? Johnson still has great value at a bargain price. If you can bring him in for someone like Doug Martin or Fred Jackson you should do it. Having Johnson as a WR3 is great.
Seek: Jeremy Maclin - He clearly hasn't been himself with his hip injury, putting up terrible numbers ... yet Vick is finally settling down, defenses are going to start shifting to guard against McCoy's & Vick's legs ... and focusing coverage on DeSean Jackson & Celek. With the relatively early (week 7) bye week, Maclin should soon be fully rested & facing loosened coverage. (Thanks to qp0n for this awesome write up)