Montero undergoes MRI on injured left thumb

CHICAGO -- Cubs catcher Miguel Montero underwent an MRI on Saturday on his jammed left thumb, and he was not expected to be able to play on Sunday in the first-half finale.

Montero was injured in the first inning during Saturday's 5-1 loss to the White Sox, although manager Joe Maddon didn't say which play. The catcher did have to chase a wild pitch by starter Jon Lester in the first, and then threw to first when the White Sox's Jose Abreu advanced. But Montero stayed in the game through the second inning.

After his at-bat in the second, Montero told Maddon that he couldn't continue.

Taylor Teagarden, promoted from Triple-A Iowa on July 4 when David Ross went on the seven-day disabled list with a concussion, took over the catching duties on Saturday and went 0-for-3.

Ross was eligible to come off the DL on Friday, and the Cubs said they wanted to wait until after the All-Star break to activate him but may be forced to have the veteran available.

"We have to figure out the backup," Maddon said of Sunday's game.

Teagarden will be the starting catcher on Sunday against the White Sox in the final game before the All-Star break.