Chavez, who underwent surgery on the shoulder late last year, told MLB.com before the announcement that he saw shoulder specialist Dr. Lewis Yocum on Tuesday and would have an MRI on the shoulder later in the morning.
"It's frustrating," said Chavez, who also had back and left shoulder surgery after being shut down late in the 2007 season. He opened this season on the DL while rehabbing his back and wasn't activated until May 29.
"I just want to get to the point where I can get out there and know I can be a productive player, and right now I'm not," he said.
In the press release announcing the Chavez move, the A's said his right shoulder surgery in November 2007 was "to repair a torn labrum." Chavez, 30, said the surgery "didn't fix anything."
"They just went in and cleaned it up. Nothing was repaired."
Chavez said his shoulder hurts more when he tries to throw than when he swings a bat, and the two movements cause different kinds of pain.
"I'd describe it more like 'electrical,'" he said. "It's like a shooting pain when I throw. When I hit, it's just like a weakness, and obviously it affects how productive I can be."
This will be his first MRI on the shoulder since the surgery.
"I don't know if I'm going to need another surgery of what," Chavez said. "I just know that it's not right, and we need to find out exactly what's wrong.
Chavez started 23 of the A's 30 games following his return, including 16 at third base and seven at designated hitter, and hit .247 with two home runs and 14 RBIs. He missed all three games of the San Francisco series last weekend and started each of the first two games of the three-game series here against the Angels. This is Chavez's third stint on the DL since July 27 of last year.
To fill Chavez's spot on the roster, the A's promoted first baseman Wes Bankston, who was batting .275 with 14 home runs and 51 RBIs in 70 games for Triple-A Sacramento.
He was leading the River Cats in hits (74) and ranked second in doubles (16), home runs and RBIs. A 24-year old right-handed hitter, he'd had appeared in 38 games at first base, 27 at DH and six at third base.
Bankston, who got the news after Sacramento's game Tuesday night and caught a 6:30 a.m. flight Wednesday to meet up with the A's, batted.378 (25-for-66) with six home runs and 18 RBIs over his final 16 games with Sacramento.
"I'm sure he's excited to be here," said A's manager Bob Geren, "and I'm excited to see him hit."
Bankston, a fourth-round pick of Rays in 2002, was claimed off waivers by Kansas City on Sept. 21, 2007, before the A's claimed him off waivers on Nov. 28, 2007. He will be making his Major League debut after batting .278 with 106 home runs and 447 RBIs in 670 games in seven Minor League seasons.
"I tried to call my parents after they told be I was going up," Bankston said, "but they were asleep."
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.