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4/15/2013 10:30 P.M. ET

Rosales, Nakajima close to starting rehab assignments

OAKLAND -- Already two weeks into the regular season, the A's have yet to send out Adam Rosales and Hiro Nakajima for a rehab assignment.

That time may be coming soon for the infielders, who suffered injuries during the last week of Spring Training.

Rosales, who is nursing an intercostal strain, may be ready for one as soon as Thursday, when the team departs for Tampa, as long as he is no longer experiencing pain when throwing across his body.

Nakajima (hamstring) may not be too far behind him, but he needs to show he can run the bases first before he returns to any game action.

"If he runs the bases this weekend, then maybe we're closer with him as well," manager Bob Melvin said Monday. "You have good days and bad days, and there are days he hasn't felt great. When we were on the road trip, I think there were a couple days he wasn't making progress, but here recently he's said he feels very good, so I think we're on the verge of getting him on the bases. We'll have a better indication of where he is once he does that."

A's honor Robinson's contributions to baseball

OAKLAND -- The A's joined forces with Major League Baseball on Monday to celebrate Jackie Robinson Day and honor the legacy of the legendary Hall of Famer.

For the fifth consecutive year, on the 66th anniversary of Robinson breaking baseball's color barrier, all players and on-field personnel donned Robinson's No. 42. Prior to the game in Oakland, two local Jackie Robinson Foundation alumnus scholars threw out the ceremonial first pitches.

In 1997, under the direction of Commissioner Bud Selig, Robinson's No. 42 was retired across all of Major League Baseball in an unprecedented tribute.

"I've always been very aware of Jackie Robinson," manager Bob Melvin said. "Not only is he one of the more impactful people ever in sports, but maybe ever in the country, period. He's opened a lot of doors. You'll hear people, especially baseball players, compliment and admire what he had to go through, and just a remarkable human being."

According to USA Today, four teams opened the season without a black player on their rosters: the Cardinals, Giants, Mariners and Rangers. Moreover, Major League Baseball says black players composed just 7.7 percent of Opening Day rosters and disabled lists. The A's have three African-American players -- Coco Crisp, Chris Young and Michael Taylor -- on their active roster, along with a pair of black coaches in Chili Davis and Tye Waller.

Such diversity extends to Oakland's front office, as well.

"We have all kinds here, and I think it's great, and I think the more diversified you are, the better off you are," Melvin said. "You learn that much more about people, and from our front office to the players, we feel like we're well represented amongst a lot of different types, and I for one am proud of the fact I'm part of that."

Freiman, Melvin react to tragedy in Boston

OAKLAND -- Though more than 2,500 miles removed from the horrific scenes in Boston on Monday, several A's players expressed deep concern over those affected by the tragedy.

Perhaps no one else was attached to the news more, though, than first baseman Nate Freiman, who grew up in Wellesley, Mass., the halfway point of the Boston Marathon.

Freiman and his family always picked out a spot downtown to watch runners make their way through the area each year, before making their way to Fenway Park for the Red Sox's annual 11 a.m. Patriots' Day contest.

"It's such a huge deal, a big day there," said Freiman, who was in constant contact with friends and family members all day. "It's just awful what's happened."

Manager Bob Melvin played in the Patriots' Day game with Boston in 1993 and, he also stressed the significance of a day that might not ever be remembered the same way, saying, "It's a big deal, a real big deal there."

"Obviously, our hearts go out to everyone in Boston," he said. "These are the really impactful days, when you realize just how insignificant what we're doing is. Those are real-life situations that hit you pretty hard. Just awful, and our thoughts and prayers are with everyone that had to go through that."

The A's placed extra security in and around the confines of the Coliseum on Monday night, with several police dogs seen patrolling the park during batting practice.

"You want to be able to go about your everyday life," Melvin said, "but you can't help but think about what did happen and feel for those people in Boston."

Crisp returns to lineup as Reddick sits

OAKLAND -- On the same day Coco Crisp's name was back in the A's lineup, Josh Reddick's was missing.

Crisp, who missed two straight games because of a strained left groin, returned to the leadoff spot for the opener of Oakland's three-game set with the visiting Astros on Monday.

But Crisp was joined in the batting order by right fielder Chris Young -- with Michael Taylor manning left in Yoenis Cespedes' stead -- rather than Reddick, who went 1-for-13 with seven strikeouts in the weekend series against Detroit after missing the three-game series in Anaheim with a sprained right wrist.

Both his struggles and his health contributed to Bob Melvin's decision to rest him Monday, the manager said, as did the presence of left-handed starter Erik Bedard on the mound. Reddick is hitting just .108 (4-for-37) on the season.

"The temptation when you come back from an injury is maybe to do too much too early, and he's a guy that wants to be there for his team," Melvin said. "He's maybe swinging out of the zone a little bit right now to do too much, which isn't a little uncommon, and I think that's how it is for a lot of guys that aren't swinging the bat well.

"It might only take one game for him to get a few hits and then that confidence comes back. He's a very good player, so it won't be long before he starts swinging again."

Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.