A Colorado Rockies starting rotation that was already being asked to improvise early in the season following the loss of Chad Bettis will likely have more impromptu changes coming as No. 1 starter Jon Gray left Thursday’s game in San Francisco after aggravating a left foot injury suffered in Spring Training.

Gray pitched three scoreless innings, allowing one hit and two walks, before exiting Thursday’s 3-1 Rockies win at AT&T Park in San Francisco. Gray missed time late in Spring Training because of a left big toe injury, but rebounded to make three starts in the regular season, including the season-opener. Although he is yet to earn a decision this year, Colorado is 3-0 in games started by Gray.

Gray received X-rays following the game and will be re-evaluated on Friday, according to Nick Groke of the Denver Post.

Manager Bud Black would not speculate postgame whether or not Gray will be ready to start his next game. Gray’s turn in the rotation is due up on Wednesday in Los Angeles. Colorado has an extra rest day on Monday, and another on Thursday of next week.

According to the Rockies’ ace, rest is exactly what he needs.

“I just have to stay off it and give it some rest,” Gray told reporters in San Francisco after the game. “If I were to try to run right now, it would be tough.”

Gray, 25, was 10-10 for Colorado last season in 29 starts. His 168 innings pitched in 2016 were second only to Bettis. With both Gray and Bettis (who is battling cancer) out of the rotation, Colorado is without a pair of starters who accounted for 354 innings pitched and 24 wins last season.

Chris Rusin, who pitched 3.1 innings of solid relief to earn the win on Thursday, is the most likely candidate to replace Gray in the rotation short-term.