Evan Gattis was sent down by the Braves on August 30th and then called up on September 3rd. He hit a HR in his first game back and I think he's someone to take a flier on if you need power. He's especially valuable in a league with daily transactions and lineup changes. He probably won't play every day so make sure he's in the lineup before you decide to play him. Gattis is batting cleanup against the Phillies today.
Taijuan Walker will likely start on Monday against the Astros and should be owned and played in all leagues. He has dominant stuff but it's questionable as to how many more starts he will make this season. He'll be an extremely popular sleeper in next year's fantasy drafts.
Johnny Hellweg will start tomorrow against the Cubs. He isn't worth a pickup in any format if you're at all concerned about your ERA or WHIP. I have to say that I am extremely impressed by Hellweg. Somehow he had a 3.27 ERA in his last ten AAA starts while having a 41:37 K:BB ratio. He has a 3:10 K:BB in 4 MLB games this season. He certainly profiles as a future middle reliever, not a starting pitcher.
Michael Wacha was recalled to start on Tuesday against the Reds and pitched very well. He'll face the Pirates on Sunday and should be owned in all formats and started in any matchup as long as he's in the Cards rotation. He's probably going to provide great value in next spring's drafts.
Scott Baker will make his season-debut on Sunday against the Brewers. I think it's best to avoid him for the rest of this season outside of NL-only formats. Baker had a 6.17 ERA in 6 class-A starts but has pitched much better in his last 3 outings.
Chris Owings will likely get sporadic playing time at shortstop for the Diamondbacks this month. He hit .330 with 12 HR and 20 SB at AAA and should provide solid value if he can earn regular playing time.
With Ike Davis likely out for the rest of the season I really like Lucas Duda's fantasy value right now. He'll likely bat cleanup on most days he's in the lineup and will start against RHP. He's eligible at 1B and OF in most leagues. Duda has 7 hits with 1 HR and 4 RBI in his last 4 games.
Alex Presley has been batting leadoff for the Twins and is worth a pickup if you need runs, batting average, and SB. He is a low-end OF option but should provide at least some value in AL-only or really deep mixed leagues.
Sonny Gray is earning the trust of many fantasy owners with his solid performance of late. He'll face the Twins next Wednesday and is certainly worth a pickup for that outing. Since August 10th he has had 5 strong fantasy starts and only one poor outing. He has a 38:10 K:BB in those 6 starts. I'll be putting Gray in my lineups the rest of the way and targeting him as a SP sleeper in next year's drafts.
Starlin Castro has his .284 with 2 HR in 74 AB in the leadoff spot and .268 with 6 HR and 7 SB in 339 AB in the 2-hole this season. He's been absolutely dreadful elsewhere in the lineup. He should continue to hit leadoff for the remainder of the season.
Johnny Cueto is nearing a return. He'll join the Reds bullpen at first but might get 1 or 2 starts in the last week of the season.
Roy Oswalt has a chance to start Sunday against the Padres in San Diego and would be a decent streaming option if he does in fact get the start.
Josh Fields has pitched quite well since August 12th and is the leading candidate for saves in the Astros bullpen right now. He's still only worth adding and putting in your lineup if you are extremely desperate for saves. The Astros don't provide many save opportunities and Fields is liable to blow up at any time.
Pedro Strop might get some save chances in the final month of the season and should be the Cubs closer in 2014 unless they make a free agent acquisition. For those owners really desperate for saves, consider adding Strop right now.
Jason Grilli made his return and pitched well. After one more solid outing he should be reinstated as closer however I wouldn't expect him to pitch more than two days in a row for the rest of the season.
Starling Marte will likely be out until the last week of the season. The Pirates figure to be cautious with him but will likely want him to play in a few games before the playoffs begin.
Allen Craig will probably be out for at least the next ten days after spraining his foot. He's currently wearing a walking boot.
Joe Mauer will likely be shut down for the rest of the season due to effects from his concussion.
Justin Masterson might miss the rest of the season due to his oblique injury.
Jose Bautista will miss the rest of the season. This is a huge blow to owners trying to make a last-second push or make a H2H playoff run. If a team doesn't have anything to play for then expect them to be overly safe and cautious with their injured players between now and the end of the season.
Peter Bourjos hasn't been providing much fantasy value lately and is apparently continuing to be affected by his wrist injury. I think that the Angels will be smart and shut him down for the rest of the season.
Josh Reddick could return in about 10 days but since he is dealing with a wrist injury he might hit for less power upon his return. If you have other options then I suggest exploring them.