Bobby Valentine was told by Red Sox upper management recently that Will Middlebrooks was strictly a third baseman. That changed on Thursday afternoon when the prospect took ground balls at shortstop, while also working on double-play feeds with Mike Aviles. Dustin Pedroia is sidelined with a thumb injury, so Boston might need depth in the middle infield. "He was also a good high school shortstop," Valentine said of Middlebrooks. "He can play another position, and if something happens, he's going to take a grounder at shortstop because Mike has played second."