Oakland Athletics right-hander Sonny Gray has been scratched from his start against the Toronto Blue Jays because of back spasms.

Right-hander Jesse Chavez will start against his former team in place of Gray on Thursday afternoon. Chavez pitched in nine games for Toronto in 2012. He is 6-11 with a 3.73 ERA.

Gray is the AL ERA leader at 2.06 and will miss his start against the highest-scoring offense in baseball. Toronto, which has won 10 straight, leads the major leagues with 611 runs this season. The New York Yankees are second with 534.

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Gray is 12-4 in 23 starts and has lost just once in his past 10 outings.