The trade came with St. Louis struggling at 32-37 and the Tigers tied for the AL Central lead. The Tigers will receive a player to be named for Maroth, who had an arm operation last year.

"Mike is a young pitcher who we feel is only going to get stronger as he continues his recovery from last season's surgery," Cardinals general manager Walt Jocketty said. "He is an established starter who is going to provide us with innings and help take pressure off of our bullpen. We think the change in leagues will also benefit Mike."

The 29-year-old Maroth was 5-2 with a 5.06 ERA in 13 starts. The Tigers have a surplus of starters, and Kenny Rogers was set to rejoin the rotation Friday night after coming back from a blood clot in his left shoulder. Detroit activated him before the game.

St. Louis has been at a loss with its starters since winning the World Series. The Cardinals said Maroth likely will have his debut for his new team next week in New York.

Ace Chris Carpenter and Mark Mulder are rehabilitating from injuries and not expected back soon, and Braden Looper recently joined them on the disabled list.

Earlier this week, the Cardinals signed Tomo Ohka to a minor league contract. He was 2-5 with a 5.79 ERA when Toronto released him.

Justin Verlander, Jeremy Bonderman and Rogers are Detroit's top three starters, and Maroth, Chad Durbin, Nate Robertson and others had been competing for the other two slots in the rotation.

Maroth went 5-2 last year while missing more than half the season after surgery to remove bone chips in his left elbow. He was not on the Tigers' postseason roster.