Chris Carpenter, RP
Boston's bullpen is already full of useful bits, but when rosters expand in September, it's going to get that much more help. Chris Carpenter is on the 40-man roster, and will likely get the call to Boston at some point next month because of it. While his control is as Carpenterian as ever, so are his strikeout rates. In his 13 innings, split between a rehab assignment and an actual stint at Pawtucket, Carpenter has struck out 14 batters while walking 7. He hasn't allowed a run to score since July 22, though, or nine appearances and nine innings ago. You can thank the four hits he held the opposition to for that.
It's not a given that he's with the Red Sox on the big-league roster in 2013, despite being 27 years old. He needs to trim some of the free passes out of his walk rate before that's a viable solution, but he'll get a chance to show what he can do about major-league hitters next month, and likely in the spring, too. Well, what passes for major-league hitters in the spring, anyway.
Zach Stewart, SP
You'll notice a theme here today, in that all of the players involved are on the 40-man, and all will likely end up in the Boston dugout in a matter of weeks. Zach Stewart might be the most intriguing of the bunch, as, if Aaron Cook ends up traded after being placed on waivers, he's the next closest thing to a major-league starter already on the 40-man roster, but not in the majors. This would be relevant, despite Cook being the extra starter on the club, because Boston isn't likely to use Felix Doubront every turn in the rotation from here on out.
Stewart has recovered his peripherals a bit after an odd beginning to things where he struck out all of five batters in his first 18-plus innings with Pawtucket. He struck out eight hitters against zero walks in five innings to close out July, and has a total of 14 strikeouts against a pair of walks in his last 15 innings, all with just three runs scored against him.
His major-league career has featured far uglier ERA, but he's got good stuff, and Boston has had a good run on arms like his that have the capability but not the results. He'll likely get a chance to show that off a bit in September.
Che-Hsuan Lin, OF
Lin is the other outfielder on the 40-man in Pawtucket, besides Ryan Kalish. He's already had a brief stint in the majors in 2012, but it was just as a placeholder until they could find a replacement for not just Jacoby Ellsbury, but Jason Repko, too. While his line is finally getting to the point where it's what you expect from Che-Hsuan Lin, it still hasn't moved past the point where he's just a bench outfielder. Albeit a bench outfielder with incredible defense, quality baserunning, and the ability to draw a walk or put the ball in play.
There's absolutely a use for that kind of player in the majors, although it might not be in Boston, given that they currently carry backup outfielders like Ryan Sweeney, thanks to their deep pockets. In September, though, in a season in which the aforementioned Sweeney is out for the year, Lin could step into games, likely in the late innings, but maybe he sneaks in a start or two as well before things are done.