"It's been bothering him for a while," Blue Jays manager John Gibbons said. "I don't know exactly what happened, but it flared up. I think he just got jammed one time real bad. ... It has been aggravating him, and hopefully it's not too long."
Prior to Saturday afternoon, Donaldson had appeared in all but one of Toronto's 56 games this year. He played through a right calf injury earlier in the season, and the only game he missed was on May 18 against the Rays for what the club described as a "day of rest."
Donaldson is hitting .254/.358/.507 with 13 home runs and 30 RBIs this season. He had a six-game hitting streak snapped in Toronto's victory over Boston in the series opener.
The future is bright Rule 5 Draft pick Joe Biagini has become an integral part of Toronto's bullpen, but his future could entail a stint in the starting rotation. The Blue Jays are not going to make the change this year, but next season, he could be considered for one of the five starting spots.
The 26-year-old entered Saturday with a 3-1 record and a 1.25 ERA over 21 2/3 innings. He began the year as a long reliever, but he has since become one of Toronto's primary setup men for closer Roberto Osuna.
"I've thought about it, and I've mentioned it to Pete [Walker, pitching coach] and front-office guys," Gibbons said. "It never really goes anywhere because he's doing his role right now, but I don't see why he couldn't do it. It won't happen this year, I don't think, but he has been impressive."