Luzardo, who took the loss in the 8-4 defeat to the Baltimore Orioles, bumped his hand on a table while playing the game, Melvin said. The Athletics staff determined Luzardo could pitch, but an X-ray showed a hairline fracture in his pinkie after the game.
The Athletics have placed Luzardo on the injured list and recalled left-hander Adam Kolarek from their alternate training site.
Oakland is getting first baseman Matt Olson back in the lineup Sunday. Olson had missed three straight games after being hit in the left eye by a ball that ricocheted off the L-screen during batting practice Thursday.
Luzardo, 23, gave up six runs on five hits, two walks and two wild pitches in three innings against the Orioles, although only three runs were earned. He is 1-3 with a 5.79 ERA in six starts this season.
The Associated Press contributed to this report.