Anderson has a sore left elbow and Ellis strained his right hamstring Monday night against the Baltimore Orioles. With Ellis out, the A's selected the contract of former top draft choice Jemile Weeks from Triple-A Sacramento.
Weeks, the 12th overall pick in the 2008 draft, was poised to make his major league debut Tuesday night against the Orioles as Oakland's leadoff hitter and second baseman.
"I'm not sure what it's going to be like up here," Weeks said before batting practice. "Got a little bit of nerves in me right now, but that's expected. Just hope to be out there and be able to calm down a little bit before the game starts."
Weeks said he expected his mother, father, sister and agent to be in attendance.
To make room for Weeks on the 40-man roster, Oakland moved pitcher Dallas Braden from the 15-day DL to the 60-day DL.
The A's also recalled left-hander Bobby Cramer from Sacramento. It's his third stint with Oakland this season.
"It's just part of baseball. It's a long season," Cramer said.
Anderson is 3-6 with a 4.00 ERA and was coming off successive poor starts against the New York Yankees and Boston Red Sox. He was sent home to Oakland on Monday and is scheduled to see the team orthopedist this week.
Ellis was batting .213 with one homer and 15 RBIs in 58 games. He missed a month last year with an injured left hamstring but said this injury was not as serious.
"This is not even close to being the same thing," Ellis said, adding that he expected to return after 15 days.