TORONTO -- While Gustavo Chacin's injury isn't considered serious, the news certainly wasn't good for Toronto. An MRI on Chacin's left arm revealed a mild sprain of the ulnar collateral ligament in the elbow and a strain of his forearm.

It hasn't been officially announced, but it appears that Chacin could be headed for the 15-day disabled list. Toronto's five-game winner will certainly miss at least one start in order to recover from the injury that forced him out of Wednesday's game after three innings.

"I'd be leaning that way," said Toronto manager John Gibbons, referring to placing Chacin on the DL. "You've got to make sure he's good and ready, but we'll see. ... I don't know if we'll have to DL him or not, but we don't want to push it."

Chacin will take a few days off before attempting to throw again. As of right now, Toronto has listed his status as day-to-day.

"Hopefully, in the next couple of days, I get treatment and get better and can come back to the mound," Chacin said. "I can't say that right now [if I'll go on the DL]. I just have to wait. I've got to play catch and see how it feels."

If Chacin, who is 5-1 with a 5.31 ERA, does land on the DL, Gibbons said that rookie reliever Francisco Rosario could move into the rotation. Rosario has been primarily a starter throughout his Minor League career, and the 25-year-old Dominican is 1-0 with a 0.00 ERA in two games out of the bullpen for the Blue Jays this season.

Other than Rosario, Gibbons said that Toronto would likely have to look to the Minors for another replacement. The Jays' manager has noted several times that reliever Scott Downs, who has served as a starter in the past, wouldn't be an option.

Chacin's injury complicates an already shaky starting staff. A.J. Burnett remains on the 15-day DL with a right elbow injury and isn't expected back for possibly another month. Josh Towers is 0-7 with a 10.09 ERA and the Jays haven't promised him anything more than one more start on Sunday. After that, he could face a move to the bullpen if his struggles persist. Also, Toronto already has one rookie, Casey Janssen, in the rotation.

Gibbons was just pleased that the news regarding Chacin's injury wasn't any worse.

"That's huge because it shows there's no serious damage," Gibbons said. "We'll just baby him a little bit and get him back strong. That would've been a big blow if it was anything more than that."

Bullpen moves: Toronto didn't believe Jason Frasor would remain in the Minors very long and that expectation came to light on Thursday, when the right-hander was recalled from Triple-A Syracuse. Frasor was optioned to the SkyChiefs on April 28.

To make room in the bullpen for Frasor, the Jays optioned Dustin McGowan to Syracuse, where he'll begin serving again as a starter -- something he has done primarliy in the past, but not this season. Toronto manager John Gibbons said that McGowan could be an option to join Toronto's rotation, but that he needs time to adjust to throwing multiple innings again.

"You really don't know what's going to happen, but also, [McGowan] needs to get some innings under his belt at this stage of his career," Gibbons said. "That way he can get out there and he can get all his pitches going. He could [be called up to start], but he still needs a little time to build up with that. We could go either way with him."

Frasor's numbers: Toronto wanted to give Frasor some time in the Minors to work on some of the issues he was dealing with earlier this year for the Jays. In nine relief appearances for Toronto, he posted a 10.24 ERA after giving up 11 runs on 13 hits in 9 2/3 innings. Frasor also had seven strikeouts and seven walks.

Frasor, who arrived to Rogers Centre around noon on Thursday and was available to pitch against the A's, has done much better since being sent down. In four games at Triple-A, he was 1-1 with a 1.50 ERA. Frasor struck out 11 and issued four walks with five hits allowed in six innings of work.

In the books: Rosario pitched two scoreless innings to earn his first Major League victory for Toronto on Wednesday. The right-hander struck out three and allowed one hit in the outing. Because Chacin only lasted three innings, it was the official scorer's decision to give Rosario the win instead of McGowan, who appeared before Rosario in the fourth inning.

"When you first go to the big leagues and you have an arm like that, if you gain some confidence, there's no telling what might happen," Gibbons said on Wednesday. "That's his first big league win and that should go a long way. He's an impressive kid."

In his first Major League game on Saturday, Rosario pitched one inning and struck out the first batter he faced.

Quotable: "They all need one. It's been a tough stretch without having a day off." -- Gibbons, on giving center fielder Vernon Wells the day off on Thursday

Coming up: Toronto right-hander Casey Janssen (1-2, 3.63 ERA) will take on Tampa Bay righty Seth McClung (1-4, 6.81 ERA) in the first game of a three-game set against the Devil Rays at 7:15 p.m. ET on Friday at Tropicana Field. The series against Tampa Bay kicks off a 10-day, nine-game road trip.