"I think that's an easy choice," O'Shea said Wednesday.
"He missed a game so if he's in for that game he probably throws for over 4,000. He won us a bunch of games early. He's been a good player for us, very good. He's the guy you build everything around."
Willy is a former Saskatchewan backup pivot who made his debut as a starter this season with the Bombers and has already passed for 3,747 yards. That's good for second on the CFL's passing list behind Toronto's Ricky Ray.
Willy will start again Saturday when the Bombers (6-11) bring the curtain down on their disappointing season in Calgary against the Stampeders (14-2). This is the third season in a row the Bombers have missed the playoffs.
The Bombers saw their faint playoff hopes disappear last Saturday when they dropped a 28-23 decision to the B.C. Lions.
Despite their problems, they've had some outstanding performances from some players besides Willy.
Receiver Clarence Denmark has followed through with his pre-season promise and topped 1,000 yards for the first time in his four years in the CFL. He's currently at 1,022 yards, second only to Edmonton's Adarius Bowman.
The Bombers also scored big in rookie kicker Lirim Hajrullahu. The native of St. Catharines, Ont., came out of Western and his 141 points are good for third on the CFL kicking points list right now.
And if that wasn't impressive enough, he's had to handle punting duties as well because of Mike Renaud's injury issues. Hajrullahu has averaged a respectable 43.8 yards a punt.
O'Shea acknowledges both, despite favouring Willy for the team's top honour.
"Clarence Denmark's had a very, very good season. Without throwing the ball, he doesn't get those yards, right?" he said of his top receiver.
Denmark's performance has been all the more important to Winnipeg with high-profile free agent signing Nick Moore out of action for much of the season with injuries.
"(Hajrullahu's) done very well for us, we put him in some tough positions too, asking him to punt on no notice," O'Shea said of his rookie kicker. "He's proven to be a professional. It's good to have him."
Denmark certainly isn't crowing, or even looking forward to next season yet, with Calgary still in his sights.
"Not yet, we're really trying to focus on this game," said the soft-spoken native of Jacksonville, Fla.
"Next season will come but we don't want to just lose again. We want to end the season on a positive note."
Hajrullahu added that he may be happy with his rookie year but he can do better, and Winnipeg's losing record is something that must be overcome.
"I think we could have done better as a team," he said.
"I mean, it sucks not being in the playoffs and I'm a very competitive guy so this is definitely a disappointment for me. Personally I think I've done well but sometimes well isn't enough. I still have different places where I can improve and I'll be working on those in the off-season."