Bruce Arians admitted Jameis Winston "has a habit of trying to be Superman" after the Tampa Bay Buccaneers quarterback endured a game to forget in London.
Winston threw five interceptions and also had two fumbles - albeit he recovered possession on the first one - as the Carolina Panthers capitalised to record a 37-26 triumph at Tottenham Hotspur Stadium.
The first overall selection in the 2015 draft was picked off to abruptly end his team's opening drive, while his second fumble coughed up the ball just as Tampa Bay were in position to score before the end of the first half.
Arians felt Winston was guilty of not throwing the ball away in that situation late in the second quarter, instead opting to hold on in the hope of producing something special.
"Throw the damn ball away. He had avoided one [turnover after losing the ball], you might have avoided two, but you aren't throwing it anywhere to a receiver. Throw it away," Arians told the media after the game.
"He has a habit of trying to be Superman. That’s been a problem in the past.
"The fumbles haven't occurred this year until today. But, again, trying to make something out of nothing. It's just a matter of knowing when to quit on a play."
Inconsistent play has plagued Winston, who is in the final year of his rookie contract with the team, throughout his NFL career.
"The fumbles - we have to get rid of those," Arians, in his first year with the Bucs, said of working with the 25-year-old. "We have to start throwing those balls away - we don't need to take those sacks, or those hits, either.
"The interceptions - I have to look back and look at the film and see where the ball was going and how it got there. I know with one of them he got hit, and the last one was just a prayer."
Asked for a response to Arians' Superman comment, Winston told the media: "Some plays I just can't fumble, I can't fumble the football. I do want to do great things, but you can do great things and protect the team."
The quarterback was also asked if he had just experienced the worst game of his career but replied: "Oh no, I've had a lot of bad games, but hopefully I'll play more good games than bad ones."
The loss in the English capital means Tampa Bay have a 2-4 record for the season.