Reyes, attempting to steal second in the sixth inning in what turned out to be an 8-4 victory over Kansas City, rolled his left ankle on his trailing leg as he made an awkward slide into second. The Jays shortstop was writhing in agony after the slide and after several minutes was taken from the field on a cart.
The Jays announced he had suffered a left ankle sprain and was taken to hospital for a MRI.
"It's a nightmare, he's a big part of this team," manager John Gibbons said. "He's the face of this team in a lot of ways. We've got to deal with it, the train keeps moving, the game keeps going on. We've got to pick up the slack."
Reyes was one of general manager Alex Anthopoulos' prized acquisitions in the off-season megadeal with the Miami Marlins.
"There's a chance where it could be a month, it could be three months," Anthopoulos said of how long he expects Reyes to be out. "I think that's going to be the range. If it's the good news you're looking at four weeks, the other scenario would be three months and if something unexpected comes up you could be looking at more than that."