The third-string quarterback who will start for the Montreal Alouettes against the B.C. Lions on Friday night is not just another new arm in the Canadian Football League.

Chris Leak was one of the most highly touted high school players in the United States before he went on to lead the University of Florida Gators to a national championship in 2006.

The 25-year-old doesn't fret over the fact he wasn't drafted by an National Football League team, or that he was cut by the Chicago Bears after signing as a free agent, or that he has spent the last three seasons as one of Anthony Calvillo's understudies in Montreal.

"I've always believed that things happen for a reason," Leak said after practice Monday. "When I look back at it, I wouldn't change a thing."

Leak became the Alouettes' quarterback when Calvillo left a game Aug. 19 against Winnipeg with a bruised sternum. He looked poised playing the entire second half of a 39-17 victory. He had tossed his first touchdown pass two weeks earlier in a brief appearance against Saskatchewan.

The usual second-stringer, Adrian McPherson, was injured in training camp and won't come off the nine-game injured list until next week.

That will leave Leak and fourth-stringer Ricky Santos as the team's only quarterbacks against the Lions (7:30 p.m. ET), although coach Marc Trestman said kick returner Tim Maypray can play quarterback in an emergency.

Calvillo, who missed practice Monday to have his injury checked by a doctor, is not expected to sit out more than one game.

Because of that, Leak gets his first start as a pro, and his performance could determine whether he will pass McPherson as the backup.

"When you're out there with your teammates and the coaches believe in you, there is no pressure," Leak said. "You just have fun playing the game you love.

"I've been blessed to play this game. Being as young as I am, I've been a part of a lot of championships."

They include state high school championships back home in Charlotte, N.C., plus his role as the starter in Florida's 41-14 upset of Ohio State in the 2006 BCS national championship game.

Although he didn't play, he was also part of Montreal's Grey Cup championship last November.

"Coming in as the starter is a little different than coming in as the backup -- everybody's looking to you," said Alouettes offensive co-ordinator Scott Milanovich. "Chris knows he's not in it by himself, but the key is how he handles the spotlight.

"One of the plusses is that Chris has been on probably a bigger stage than he'll be on Friday night, so it should not overwhelm him."

Leak is considered mostly a drop-back quarterback with a rifle arm, much like the 37-year-old Calvillo, except that he has younger legs to scramble in the backfield or take off with the ball when needed.

Leak signed with the Hamilton Tiger-Cats in 2008 but couldn't attend camp due to an injury. The Ticats released him and Alouettes general manager Jim Popp put in a claim the next day.

"He's an unbelievable student of the game," said Popp, who gave Leak's older brother C.J. a tryout in 2005. "Leak wants to be a coach when he stops playing, he told us that, but he says he wants to play first."