First baseman, Kennys Vargas (Twins): The rookie slugger is not slowing down, as he has driven in seven runs in his past three games. With 31 RBIs in 32 games since joining the Twins, he should have forced his way into all fantasy lineups by now.
Second baseman, Mookie Betts (Red Sox): The Sox have finally given Betts the playing time he deserves, and the 21-year-old is in the midst of a full-scale breakout. He has picked up three homers, two steals, eight RBIs and seven runs scored in his past 10 games. There are few players on the waiver wire who will be a better source of five-category production in September.
Shortstop, Jose Ramirez (Indians): Ramirez is one of the biggest reasons that the Indians have surged in the playoff race after trading away Asdrubal Cabrera at the end of July. In his past 10 games, the 21-year-old has five multihit efforts, seven runs scored and three steals. He is a great source of cheap speed at a premium position.
Third baseman, Luis Valbuena (Cubs): Perhaps it is because of his age, but Valbuena's recent power surge is being dismissed by most fantasy owners. Smart owners will take a second look at the 28-year-old, as he has smacked eight dingers since the beginning of August.
Outfielder, Adam Dunn (A's): There are few players on waivers who possess as much raw power as Dunn. The lefty slugger could be revitalized by a recent trade to a contender, as he went deep in each of his first two starts with the A's. If Dunn could hit .240 with a six dingers in September, he would help clubs that need power.
Outfielder, Dayan Viciedo (White Sox): Viciedo picked the right time to heat up, as he has smacked three homers in his past four games. The late-August trade of Alejandro De Aza opens up more playing time for the 25-year-old, and if he can take advantage of the opportunity, he could carve out a larger role for the coming season.
Outfielder, Juan Lagares (Mets): Lagares promised to be more aggressive on the basepaths, and so far he has delivered, with five steals in his past six games. The 25-year-old lacks power, but he can hit for average, which makes him more than a one-category contributor if he continues to rack up steals.
Starter, Miguel Gonzalez (Orioles): The 30-year-old is pitching as well as just about any starter on waivers in mixed leagues, and he is lined up for a pair of starts next week. Gonzalez has allowed just four earned runs in his past four outings, and he has a 21-to-4 strikeout-to-walk rate over that stretch.
Starter, Josh Collmenter (D-backs): Like Gonzalez, Collmenter is a surging starter who happens to line up for two starts next week. The 28-year-old has allowed two runs on 11 hits and two walks over his past three outings, and he should have success against the Giants and Padres in the coming stanza.
Starter, Marcus Stroman (Blue Jays): This rookie is not slowing down late in the season, as he has allowed three earned runs over his past two starts. Stroman will work at home twice next week, and he could rack up K's against the Cubs before facing a Rays squad that he defeated on Wednesday.
Starter, Danny Salazar (Indians): Since rejoining the Tribe's rotation in the second half of August, Salazar has allowed three earned runs over four starts. His excellent work culminated with a shutout of the Tigers on Wednesday. Salazar owns a strong strikeout rate, and he should produce plenty of K's in his upcoming two-start week.
Starter, Jon Niese (Mets): The lefty has not pitched well in the second half, so it will require a leap of faith to start him in mixed leagues. The schedule is aligned for Niese to turn things around, as he will make a pair of home starts in pitcher-friendly Citi Field against the Rockies and Nationals. He has notched a quality outing in his past three home starts, and the Rockies could struggle on the road, especially without their two best sluggers.
Starter, Trevor Bauer (Indians): Bauer has been inconsistent this summer, but he has thrown 11 2/3 shutout innings in his past two starts. The right-hander should provide plenty of K's next week, but his 1.40 WHIP shows that he should be used only by owners with some wiggle room in that category.
Starter, Mike Leake (Reds): Leake is yet another starter who is pitching well and is also scheduled for two starts in the upcoming week. The 26-year-old has not allowed a run in his past two starts, and he should have some success at home against the Cardinals before hitting the road to take on the Brewers.
Reliever, Kevin Quackenbush (Padres): Closer Joaquin Benoit has not pitched since Aug. 26 due to a shoulder injury, but because of the expanded rosters in September, the Padres have little incentive to place Benoit on the DL. Fantasy owners who need saves can take a chance on Quackenbush, who should be able to handle ninth-inning duties until Benoit is ready to return.
Reliever, Eric O'Flaherty (A's): O'Flaherty had the misfortune of taking over the team's closer role just as they went on a notable losing skid. But the A's have enough talent to turn things around quickly, and the lefty could rack up saves in bunches in the coming days.