The injury occurred during a play at the plate on July 1 against the Los Angeles Angels. Mora missed six straight games, then received one at-bat as a pinch-hitter the day before the All-Star break.

He started Thursday night but left after one inning. After undergoing an examination yesterday, Mora said he would be out for at least a week. Instead of biding their time while he worked to return, the Orioles thought it best to place him on the DL.

"You don't want to play short-handed and it gives Melvin an opportunity to get right," interim manager Dave Trembley said.

Mora is batting .265 with a team-high 12 homers and 41 RBIs.

To fill the spot on the roster, the Orioles recalled outfielder Jon Knott from Triple-A Norfolk. Knott played in three games during two earlier stints with Baltimore this season, going 3-for-6 with three RBIs.

At Norfolk, Knott was batting .231, but he hit .333 in nine games in July. The Orioles had other options, but settled on Knott in part because he's on the 40-man roster.

"He's got some power. He's been up here before," Trembley said. "Let's get him back up here and see if we can give him another chance."

Knott was playing for the Tides in Ottawa when he got the word.