When Casey Janssen takes the Rogers Centre mound against Boston Friday, he expects to feel a wave of emotions running through his body.

It would be hard not to, given that the Blue Jays’ right-hander will be making his first big league appearance in Toronto since Sept. 19, 2007.

“I think it’ll be special,” said Janssen, who returned last week after missing all of 2008 with a right shoulder injury. “I’m going to try ... and focus on the game at hand, but it will be special to be back in Toronto in front of the fans. But with Boston, you don’t want to be too excited. You want to focus on your job.”

Focus is something Janssen knows all about. Anytime a pitcher has an injury to his throwing shoulder, it can be daunting. Yet, in dealing with his injury and the ensuing rehab, Janssen focused on keeping only positive thoughts.

Not once did Janssen, 27, entertain the thought his torn labrum could end his career.

“I think it can overwhelm you if you aren’t positive and it could maybe end your career if you have the ‘why me’s?’ or feel sorry for yourself,” he said. “I just took my rehab as a challenge.

“Some people did say that it’s a lot to come back from, but I wanted to prove the doubters wrong that you can come back, hopefully even better.”

Janssen completed the rehab at home in California, where he constantly watched his teammates on television. He says that was by far the toughest part of his injury.

“Not being with the guys — the camaraderie part — was probably the hardest,” Janssen said. “Just sitting there watching and being helpless if the team’s struggling.”

Janssen is finally back with his teammates, who are hoping he will add stability to Toronto’s starting staff. Armed with what he calls a new appreciation for his career, Janssen says the injury also taught him a lesson.

“I’ve learned I’m mentally strong,” he said. “I’m able to take the good and bad times the way they are thrown at me, and try to make the most of them.”

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