Jose Iglesias will be playing third base, manager John Farrell told ESPN.com.
Farrell said no time parameters have been set for Middlebrooks.
In this season’s sixth game, Middlebrooks hit three home runs against the Blue Jays in Toronto, but then sank into an extended slump in which he had just five hits in 54 at-bats (.093).
He also injured his ribs in a collision with catcher Ross on May 7, and on May 24, Middlebrooks went on the disabled list with a lower-back strain, missing 16 games.
DIAMONDBACKS: Eric Hinske’s suspension for participating in a June 11 brawl at Dodger Stadium has been reduced to one game from five.
He dropped his appeal and served the suspension Tuesday night when Arizona opened a three-game series in Washington. Hinske said his agent informed of him of Major League Baseball’s decision.
• The team reinstated second baseman Aaron Hill from the 15-day disabled list and optioned left-hander Joe Paterson to Triple-A Reno.
Hill hit .306 the first 10 games of the season before breaking his left hand after being hit by a pitch thrown by Pittsburgh’s James McDonald on April 9.
NATIONALS: Outfielder Bryce Harper was set to begin a rehabilitation assignment Tuesday night as he recovers from left knee bursitis that has sidelined him for nearly a month.
Manager Davey Johnson said that Harper, who hasn’t played since May 26, likely won’t rejoin the Nationals this weekend when they travel to New York.
Harper was scheduled to start the assignment at Single-A Potomac.