Manager Brad Ausmus has a good idea of what Dirks can expect -- he says he had the same injury a few years ago.
"My understanding is a piece of the disk tore away from the whole of the disk," Ausmus said. "They're just going to go in and remove that piece and clean up the area on the disk where it had come off."
General manager Dave Dombrowski says the 28-year-old Dirks will have surgery Monday. Dirks was expected to share the left field spot with Rajai Davis, whom the Tigers signed in the offseason.
Dombrowski says Dirks has dealt with back issues for a while.
"He's had twinges there, he goes back, he says, all the way to high school," Dombrowski said. "The other day, he just said it was bothering him, and it bothered him more."
The team had him checked out by a specialist Tuesday and found out the diagnosis. Dirks hit .256 with nine home runs in 131 games last year. He hit .322 in 2012.
The Tigers did not sign Davis to be an everyday player, but he may have a chance to play more with Dirks out. Davis hit .319 against left-handers last season but only .228 against righties.
"If Rajai plays well, he may be the only guy we need," Ausmus said.
Utilityman Don Kelly can also play in the outfield, and Ezequiel Carrera could be an option as well. Second baseman Steve Lombardozzi, acquired in a trade with Washington over the offseason, has 49 career starts in left field.
Ausmus said he had this back operation in 2010, his final season as a player. Ausmus said he had surgery the first week of the season. He did not play again that year until July 24.