Buchholz had been expected to start Friday night against the White Sox. Manager Charlie Montoyo will instead use an opener, Daniel Hudson, and rely on the bullpen.
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Buchholz is the third Toronto starter go on the IL recently. Matt Shoemaker suffered a season-ending ACL tear in late April and Clayton Richard is out with a knee problem.
The 34-year-old Buchholz, who missed almost all of 2017 and half of last season with arm injuries, signed a one-year, $3 million deal with the Blue Jays for 2019. He has gotten off to a slow start, with a 6.57 ERA and 1.54 WHIP in five starts.
The Toronto Sun reported the Jays may move reliever Sam Gaviglio into the rotation to fill Buchholz’s spot.