Galarraga, acquired by the Diamondbacks from Detroit in January for a pair of prospects, was 3-4 with a 5.91 ERA in eight starts for Arizona. He had lost four straight games, including the club's 8-4 loss to San Diego on Monday. He had allowed 13 home runs in 42 2/3 innings this season.
Galarraga, best known for pitching an almost perfect game last June for the Tigers against Cleveland, is 26-30 in 95 appearances and 86 starts with a 4.69 ERA.
After what turned out to be his final start, Galarraga became heated when asked if he felt his spot in the rotation was in jeopardy.
"What are you talking about?" he asked. "What are talking about my next start, huh? What are you saying that I'm going to be worried about my next start? Huh? You saying I lost my job?"
The Diamondbacks have seven days to place Galarraga on waivers and 10 days to either trade or release him.