The manager was told the prospect was strictly a third baseman.
That could change, however, with Dustin Pedroia sidelined with a thumb injury. Middlebrooks was taking ground balls at shortstop Thursday afternoon at Fenway Park. He also was working on double-play feeds with Mike Aviles, the Red Sox's regular shortstop.
If either Aviles or Nick Punto goes down with an injury while the Red Sox were still waiting on Pedroia, the Sox would need Middlebrooks to fill in.
"He was also a good high school shortstop," Valentine said of Middlebrooks, while smiling. "He can play another position, and if something happens, he's going to take a grounder at shortstop because Mike has played second."
What's unclear, however, is whether Middlebrooks could see extended time there if Pedroia were to be placed on the disabled list.
It should be noted, however, that the Red Sox moved Middlebrooks out of the shortstop position shortly after drafting him. He was converted to third baseman in extended spring training. His manager in Lowell, Gary DiSarcina, said he looked like a "fish out of water" at short.
Valentine hinted that the Sox might make a move to add another infielder to the roster this weekend.
"I expect before the weekend is over we will have another infielder, but maybe not," he said.
When Red Sox veteran third baseman Kevin Youkilis went on the disabled list with a lower-back strain May 2, the club promoted Middlebrooks from Triple-A Pawtucket.
The 23-year-old Middlebrooks has been solid offensively and defensively during his time in the big leagues, posting a .316 average with six homers and 21 RBIs in 24 games. Because of his success, it's been an extremely difficult decision for Valentine to remove the youthful spark from the lineup.
Since Youkilis was activated May 22, the veteran has played third and first base, and Adrian Gonzalez has played right field, too, all to keep Middlebrooks in the lineup. The rookie did not play in the Red Sox' 7-3 loss to the Detroit Tigers on Thursday night at Fenway Park, and Valentine said it was a difficult decision, especially since Middlebrooks went 2 for 4 with a home run and two RBIs against the Tigers on Wednesday.
"It's all kind of tomfoolery," Valentine said.
Then the manager explained since the Red Sox will play a three-game set against the Toronto Blue Jays on artificial turf this weekend at Rogers Centre, Gonzalez won't play all three games in the outfield and will need to play first at some point during the series. Also, Youkilis won't play all three games in Toronto because of the surface.
"We're trying to keep everyone fresh and mix and match the best we can," Valentine said.