BALTIMORE — The Baltimore Orioles addressed their shaky shortstop situation by acquiring Juan Castro from the Colorado Rockies in a trade of minor league infielders today.

Castro was batting .300 in 18 games with Triple-A Colorado Springs. The 36-year-old has more than 11 years of major league experience and played in seven games with Cincinnati this season before being released in April.

He has also played for the Los Angeles Dodgers and Minnesota Twins.

"I haven't seen him play so it is too early to say what role he has," Orioles manager Dave Trembley said. "The last time I saw Juan Castro play was in the Texas League in 1993 and he was playing for the Dodgers in that league. He just got here. He's been on an All-Star break. I'd like to get a feel for what he can do and this and that and we'll go from there."

The Orioles sent Mike McCoy to the Rockies and made room for Castro on the roster by outrighting shortstop Freddie Bynum to Triple-A Norfolk. Bynum hit .179 in 40 games this season.

Bynum has 72 hours to accept a minor league assignment or become a free agent.

The shortstop position has been a problem for the Orioles since the offseason trade that sent Miguel Tejada to Houston. Baltimore has used Luis Hernandez, Bynum, Alex Cintron and Brandon Fahey at the position.

The signing of Castro, however, does not mean the Orioles are not still in the market for a full-time shortstop.

"I don't think you're ever done looking to improve your team," Trembley said.

Castro is also expected to provide depth at second base behind Brian Roberts.

In a separate move, the Orioles place pitcher Greg Aquino on the 15-day disabled list, retroactive to July 13, with a hamstring strain. To fill the void in the bullpen, the Orioles activated right-hander Randor Bierd from the DL. Bierd, a Rule 5 pick, was 0-1 with a 2.03 ERA in nine games with Baltimore before being place on the disabled list May 2 with a sore right shoulder.