PEORIA, Ariz. -- Infielder Corey Koskie, who is trying to make a comeback from a concussion that has sidelined him since 2007, had to leave Thursday's game after feeling ill.

Koskie, 35, handled back-to-back ground balls in the first inning for the Cubs against the Seattle Mariners. He stayed in the game to hit in the second and third innings, grounding out both times, and was then lifted for a defensive replacement in the bottom of the third.

Koskie played in exhibition games earlier this month in Florida with Team Canada, and was at third for four innings. On Tuesday, he played six innings at third, but in those two games, he never had a ground ball hit to him.

He has not played in the Major Leagues since July 5, 2007, when he was with the Milwaukee Brewers. Koskie suffered the concussion falling backward as he went after a popup by Cincinnati's Felipe Lopez. He signed a Minor League contract with the Cubs, who are looking for a backup third baseman.

Cubs manager Lou Piniella said they will be very careful with Koskie. Apparently when Koskie dove for one of the ground balls in the first, he had some problems, but wasn't specific.

"As soon as he said he wasn't feeling well, we got him out of there," Piniella said.