The rookie starting quarterback was sacked an offence-crippling 10 times in a 28-23 loss to the B.C. Lions that killed Winnipeg's playoff hopes.
"It was spread around the offence," O'Shea said of the mistakes that opened Willy to so many sacks.
"As Drew said in his post game, he hung onto the ball a little bit longer than he wanted to. When we watched the film there was certainly evidence of that."
He also agreed with Willy's assessment that he didn't look for open receivers as well as he should when his first target was covered.
"He hung onto his first read for longer than usual, for whatever reason."
Sacks aren't a new problem for the Bombers. They've allowed a league-worst 70.
O'Shea didn't overtly criticize his starter, in fact he praised him for recognizing what went wrong, but the coach said he will examine the season as a whole once it is finally over.
"It's not fair to the guys that are in playing for me to be thinking about that," he said.
"I've asked them to eliminate all distractions from this point forward and focus on Calgary so if their head coach isn't going to do the same, we're not going to have good direction."
Willy will be starting in Calgary (14-2) when the Bombers (7-10) bring the curtain down Saturday on another disappointing year — their third in a row on the outside of the playoffs looking in.
"Drew's going to start for sure," said O'Shea. "How that plays out after that, I don't have a good plan yet."
The game may have little meaning for either team in terms of standings — Calgary has already locked down first place in the West (and the CFL) and Winnipeg last in the West — but O'Shea insists it's still important.
"We're going in with the idea that we're going to win this game. We're going to put plans together and try and beat Calgary. . . It would be great for our team, we need that. We need to salvage something."
For a while Saturday, it looked as though the Bombers might even salvage their season.
Winnipeg went into the fourth quarter ahead 17-13. When B.C. quarterback Kevin Glenn left the game following a huge hit it looked even better, even though a playoff spot would still have required all the luck of O'Shea's Irish ancestors.
But B.C. backup John Beck stepped in and immediately threw a go-ahead touchdown, then put another in the hands of Kito Poblah, a Canadian receiver traded to the Lions by the Bombers.
Running back Paris Cotton, the only Winnipeg offensive player who really shone Saturday, managed to narrow the gap with a touchdown that capped his 131 yards rushing, but it was too little too late.
The Bombers were 5-1 in July but have lost 10 of 11 since. They are currently on an eight-game losing streak.
Fans have been waiting a long time for the Bombers to return to glory. They made a losing Grey Cup appearance in 2011 but haven't won the CFL final since 1990, the longest drought in the league.
Last year they tied their worst season record in the 18-game CFL at 3-15. They responded by cleaning house in the front office and coaching ranks.
This is O'Shea's first season as a head coach.