Gray, who originally hurt the toe during spring training, said he reinjured it while leaping to snag a high hopper in the second inning. He left the game after allowing one hit in three scoreless innings.
He had X-rays taken, but manager Bud Black said the team wouldn't know the severity of the injury until Friday morning and couldn't speculate on whether Gray will make his next start.
"I just have to stay off it and give it some rest,'' Gray said after the game. "If I were to try to run right now, it would be tough.''
In other injury news, Black said first baseman Ian Desmond, who broke his left hand during spring training, has started to play catch and take a few ground balls.
"Ian is gaining on it," Black said. "He's starting to get some clearance to up the activity. "
Black hopes Desmond, who signed a five-year, $70 million deal with the Rockies in December, can take batting practice next week, but there's still no timetable for his return.