Shortstop Stephen Drew (left hamstring tear) was officially placed on the disabled list, retroactive to Saturday, and left-handed pitcher Doug Slaten was optioned to Triple-A Reno.
To replace Drew on the roster, the team selected the contract of infielder Josh Wilson from Reno and, to take Slaten's place, right-hander Esmerling Vasquez was recalled from Reno.
Drew tweaked the hamstring a week ago Friday during a game played in chilly conditions in San Francisco. After taking four days off, he returned to the lineup, but he reinjured himself on Friday night during the first inning.
"It's frustrating when you're trying to play through something so you can help the team, but you're really not," Drew said.
Wilson, a non-roster invitee this spring, impressed the staff during camp with not just his defense, which he has always been known for, but his production at the plate. A right-handed hitter, he could get some starts against left-handed pitching, with Augie Ojeda getting the other starts at short.
"I knew that making the team was going to be tough, but the season is tough, a lot of things can happen," said Wilson, who was hitting .260 with three doubles and 10 RBIs at Reno. "The main goal is just to play well and show them that given the opportunity, I could be a guy that could come up here and help and fit in for a while, and hopefully longer than a while."
How long remains to be seen, because the team is hopeful that Drew will be ready to return when his 15-day stint on the DL is completed.
Vasquez's stay could last a lot longer. The right-hander is one of the team's better pitching prospects, and he showed this spring that he was fully recovered from a shoulder injury he sustained in the Arizona Fall League in 2007.
Vasquez, who is in the big leagues for the first time, could help the team by providing multiple-inning stints out of the bullpen. He had a 0.93 ERA with one save in six games for Reno.
"It's my dream," Vasquez said of being called up. "It's just very exciting."
Slaten has been inconsistent this year, and after moving his arm angle from over the top to more of a three-quarters look this spring, he had some success, but he found himself reverting to his old ways in his outing on Saturday.
"I haven't done what's been expected of me," Slaten said just before leaving the clubhouse. "And I'm not satisfied with it either. It's a good time for me to go down there and iron things out. This isn't the place to be doing that."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.