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6/19/2013 2:00 P.M. ET

Davis the DH for first time in '13; Ishikawa at first

DETROIT -- Chris Davis was the Orioles' designated hitter on Wednesday afternoon against the Tigers for the first time this season, with manager Buck Showalter inserting Travis Ishikawa at first base in his place.

"I'd like to do it with more guys, but there's only one DH spot," Showalter said. "It's one of the assets that Trav brings, it gives us some time to [start] Chris [at DH] here or there. You won't see it much. Usually when you got an off-day, you try to do it. I try to do the benefit of two [days], because one doesn't do much for you. … Chris has been grinding it pretty good over there."

Davis entered Wednesday with a Major League-leading 24 homers. He was batting .332 with 61 RBIs as the team's everyday first baseman. Ishikawa, who was added to the roster on Tuesday, started for the second game, as the club takes a look at the infielder. The O's will have to make a roster move to add Miguel Gonzalez from the paternity leave list on Friday, and Ishikawa -- who took Gonzalez's spot -- could be the guy to go.

Roberts runs, hopes to go on rehab assignment soon

DETROIT -- Orioles second baseman Brian Roberts ran short, speedy bursts on the field prior to Tuesday's game, the last remaining step as he progresses back from right hamstring surgery, with the goal of going out on rehab assignment next week.

"[He] did pretty well with it," Orioles manager Buck Showalter said. "I asked Brian, I said, 'What's the difference between pretty well and great?' I think sometimes it's a mentality. You had a piece taken out. Obviously it's just letting the body cover for it. ... I'm hoping when we get off this road trip, he's going out [on a rehab assignment]. We'll see."

Roberts will come in to work out on Thursday's off-day in Toronto, and he's made positive progress since joining the team in Baltimore earlier in June. Showalter said he thought being around the atmosphere of the other players has benefited Roberts, who was helped off the field on April 4.

Worth noting

• The Orioles signed seven more picks from the First-Year Player Draft to contracts on Wednesday: Trey Mancini (eighth round), Austin Wynns (10th), Randolph Gassaway (16th), Dylan Rheault (19th), Donnie Hart (27th), Justin Viele (37th) and Garrett Cortright (40th). Mancini and Wynns will report to short-season Class A Aberdeen, the rest to the Gulf Coast League.

Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.