Chulk had a 7.36 ERA in 12 games this season. Last season Chulk pitched in 62 games and posted a 3.88 ERA.
The fatal blow for Chulk was May 2 when he allowed four runs in an inning of work. Chulk allowed three runs or more in three of his twelve appearances this season.
"He was struggling," manager John Gibbons said. "He'll go down and figure it out."
Rosario went 0-2 with a 4.43 ERA in five starts at Syracuse. Manager John Gibbons said he'll pitch out of the bullpen.
"We need to find out about him before someone else does," Gibbons said referring to Rosario.
One Blue Jays official told InsideTheDome that Rosario is currently viewed as a reliever, and a spot in the rotation has not been discussed.