Following Toronto's 7-3 win over Baltimore on Sunday, Cecil said he has been instructed to wear a knee brace during his workouts and added that he will be sidelined for a week to 10 days. If everything goes according to plan, the 23-year-old will start as scheduled against the Red Sox on Aug. 20 at home.
"He's going to miss a start," Gaston said. "They didn't really see anything that's a real problem with his knee. He just strained it a little bit. Just to be safe, he won't pitch [at Tampa Bay on Saturday]. He'll miss a start, and we'll see what happens from there."
Cecil, who was told he can continue throwing between starts, said he didn't believe he would require offseason surgery.
"They didn't say anything about that," Cecil said. "In the offseason, it might just heal on its own."
The Blue Jays have a couple of options for Saturday's start against the Rays. Toronto could use left-hander Brian Tallet, who has made 18 starts this season and worked five innings in relief of Cecil. With an off-day on Thursday, the Jays also could use rookie southpaw Marc Rzepczynski on normal rest.
Cecil, who was selected 38th overall in the 2007 First-Year Player Draft, pulled himself out of his start on Saturday with one out in the fifth. The left-hander earned a no-decision, remaining 5-1 this season with a 4.35 ERA. Cecil said he first experienced pain in his left knee during Spring Training, and then once while with Triple-A Las Vegas.
In his outing against the Orioles, Cecil indicated that the issue flared up during the third inning, and by the fifth, he was having trouble pushing off the mound. On Sunday, Cecil said the problem stemmed mainly from his medial collateral ligament and that most of the discomfort was in the lower part of his knee.
"I don't really expect anything serious," Cecil said. "It's just kind of a nagging pain that's been going on. It's my left knee -- the drag leg. Every time I go to throw and drag that foot, it pulls on the inside of my knee. It's almost like I've got to pick my leg up first and then throw it, instead of pushing off."