Clint Barmes started at shortstop on Saturday. Middlebrooks, the team's starter at third base 60 times this season, wasn't in the starting lineup.
So far, Padres interim manager Pat Murphy has liked what he's seen of Middlebrooks at shortstop.
"[It's] asking him to do a whole lot, but he's just the type of guy who can do it because he's so athletic. I think it's rejuvenated him a little bit," Murphy said.
"It's a work in progress, it's not anything that's going to be easy, but he's making it look easy right now. There's a lot to learn, he knows that."
This isn't a shot in the dark for the Padres, as Middlebrooks was drafted as a shortstop by the Red Sox in 2007.
When asked if he'll use Middlebrooks more at shortstop in the second half, Murphy said, "for sure."
That means Barmes and Middlebrooks will likely see most of the playing time at shortstop. Alexi Amarista, who has started a team-high 55 games at the position, will likely play more in a "super-utility" role, Murphy said.
Middlebrooks made one start at shortstop on May 23 when Bud Black was still the manager. So far, he's handled himself well with 16 total chances without an error.
Boston-area scout Jay Oliver, who signed Middlebrooks, said he wouldn't be surprised if Middlebrooks has success at shortstop.
"He is a really good defender with great instincts, good hands and feet, plus arm," Oliver said. "He has changed a lot since he was drafted. He's probably 30 pounds bigger. I am sure moving forward he will be move of a corner infielder, but he is a good enough athlete that he can still play shortstop for a short period.
"He actually rotated over to second base a few times when he was with us and he had never played second base. He is still fairly young and learning, but he should continue to get better."
The Padres would love to see more offensive production from their shortstops. Entering Saturday, they ranked 24th in the big leagues in batting average (.238) and 26th in RBIs (24) as well as eighth in the most errors (14) this season.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.