Eight top prospects who could be called up in September

Jameson Taillon could arrive to help the Pirates secure their first postseason spot in 20 years. (Charlie Neibergall/AP) Major league rosters expand from 25

Jameson Taillon could arrive to help the Pirates secure their first postseason spot in 20 years. (Charlie Neibergall/AP)

Major league rosters expand from 25 to 40 men on Sunday, allowing teams competing for a playoff spot to add extra depth for that postseason push and for clubs no longer in the hunt for a playoff berth to take an early look at some of their top prospects. Several of those prospects made their way onto 25-man rosters in the last month or so, including Marlins outfielders Christian Yelich and Jake Marisnick, A's starter Sonny Gray, Mets catcher Travis d'Arnaud, Red Sox infielder Xander Bogaerts, Cardinals second baseman Kolten Wong and Mariners starter Taijuan Walker. Others, such as the Red Sox' Jackie Bradley Jr., and Cardinals righties Michael Wacha and Carlos Martinez, are locks to be called back up having previously, and recently, served on the 25-man roster.

Here, then, is a look at eight possible call-ups, all of whom would need to be added to their team's 40-man roster, in rough order of their chances of a promotion.

George Springer, CF, Astros

Springer won the Double-A Texas League's Player of the Year award despite playing just 73 games in that league, and was even better after being promoted to Triple-A in late June. On the season as a whole, he has hit .306/.415/.609 with 37 home runs 107 RBIs, not to mention 43 stolen bases at an 84 percent success rate. He will be the Astros centerfielder next year, and should be in September as well.

Chris Owings, SS, and Archie Bradley, RHP, Diamondbacks

The National League playoff field is largely set, but the team trailing that field by the fewest games is the Diamondbacks, who could get a boost in September from not only the previously promoted lefty Tyler Skaggs and third baseman Matt Davidson, but from top prospects Owings and Bradley as well. General manager Kevin Towers floated the latter as a potential rotation reinforcement in early July, and surely wasn't dissuaded by Bradley going 11-5 with a 1.98 ERA for Double-A Mobile. Bradley has surpassed his 2012 inning total by just 11, so he has more to give, possibly out of the bullpen. Owings, meanwhile, was named the Pacific Coast League's Rookie of the Year after hitting .326/.355/.472, and, having recently returned from a hamstring injury, could be a valuable offense-first alternative to fielding-wiz Didi Gregorius at shortstop.

Billy Hamilton, CF, Reds

Hamilton had a lousy season at the plate for Triple-A Louisville this year, hitting a mere .256/.308/.344 and seeing his unintentional walks drop from 84 to 38. Still, despite shedding nearly 100 points of on-base percentage, he still managed to steal 75 bases at an 83 percent clip one year after setting a professional baseball record with 155 steals. The Fastest Man in Baseball can play centerfield and shortstop (though he played none of the latter this year after making the move to the outfield), making good use of his speed at both positions, and has game-changing speed off the bench. Think of the famous Dave Roberts stolen base from Game 4 of the 2004 American League Championship Series, a crucial, series-changing steal at a point in the game when everyone watching knew Roberts was going to run. Hamilton can have that kind of impact if given the opportunity.

Jameson Taillon, RHP, Pirates

Having recently demoted the struggling Jeff Locke and with Wandy Rodriguez likely done for the season, the Pirates could use another starter, and Taillon, the 10th-best prospect in baseball according to Baseball Prospectus's mid-season top 50, would seem to fit the bill. Taillon was promoted to Triple-A at the start of August and has posted a 2.84 ERA in his last three starts at that level. Pittsburgh might prefer to have Taillon follow Gerrit Cole's path to the majors, which would bring him up in the middle of next season, but with the postseason finally in its sights, the temptation to promote Taillon, who is two outs shy of last year's innings total, may be too great.

Nick Castellanos, LF, Tigers

Castellanos is a converted third baseman, and while the Tigers have used him exclusively in the outfield this season, one wonders if his promotion would allow them to give Miguel Cabrera additional rest. Even if not, Castellanos' righthanded bat could improve Detroit's leftfield situation. Lefty-hitting Andy Dirks has struggled and Dirks' righthanded platoon partner, Matt Tuiasosopo, has fared better against fellow righties.

Noah Syndergaard, RHP, Mets

Syndergaard came over with d'Arnaud in the R.A. Dickey trade with the Blue Jays last December and is the third major Mets pitching prospect after Matt Harvey and Zack Wheeler. He struck out 11. 5 men per nine innings in Double-A this season with a 5.75 K/BB ratio, is expected to join New York's rotation next year. With Harvey's recent injury, there's room for him in the Mets' rotation, though one wonders if, after the perfectly managed Harvey broke down, the Mets would be willing to push their next pitching prospect at all. Still, Syndergaard could make a couple more starts before his innings exceed his 2012 output by 30 frames, so why not make them in the majors?

Yordano Ventura, RHP, Royals