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07/13/12 10:35 PM ET

Hammel exits early vs. Tigers with injury

His right knee was injured while throwing a pitch in the fourth inning

BALTIMORE -- Jason Hammel exited early from Friday's start against the Tigers in the top of the fourth inning when he to injured his right knee on a pitch to Brennan Boesch.

He will be further evaluated tomorrow.

Hammel hopped up and grimaced after throwing a ball on a 1-2 pitch to the Detroit right fielder. Manager Buck Showalter and the training staff immediately came out to check on Hammel.

They spoke with him for a few minutes, and Hammel tried to throw a few practice pitches, but they decided to pull Hammel at that point.

This could cause more problems for a Baltimore pitching staff that's been hurting in recent weeks. Hammel already had to deal with problems in his right knee earlier this season, working his way through soreness.

If Hammel's out, it would hurt the Orioles, as he's been the team's top starter this year. He was one of the five finalists for the last spot on the American League All-Star team and came into this game with a record of 8-5 and a 3.47 ERA.

He struggled at first in this game, giving up two runs on four hits in the first before settling down and giving up just one additional hit until Boesch came up to lead off the fourth. Luis Ayala replaced Hammel.

Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.