Story highlights Bernie Ecclestone believes Michael Schumacher should not have returned to F1

Seven-time champion Schumacher winless in his three seasons with Mercedes

Ecclestone says the lack of success after coming out of retirement tarnished his image

F1 supremo hails success of the 2012 season

F1 supremo Bernie Ecclestone believes seven-time Michael Schumacher made a mistake by coming out of retirement in 2010 to spend three largely unsuccessful seasons with Mercedes.

The 43-year-old German quit for a second time at the end of the 2012 campaign and will be replaced in the team by Britain's Lewis Hamilton next season.

A solitary podium spot in the European Grand Prix at Valencia earlier this year was the highlight of Schumacher's comeback and Ecclestone said the poor results have tarnished his image.

"I would rather he had stopped as a seven-time world champion than stopping now," Ecclestone told the official F1 website.

"People new to the sport -- people who have joined the F1 fan fraternity just recently -- will remember Michael now, not as he was.

"They don't see the hero that he was but the human that can fail. We will miss Michael, because even though he wasn't winning races in those three years, he is still very popular.

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"I think the important thing is -- and this is probably difficult -- to know when you can't do what you used to do anymore and then hand it over to somebody else."

Schumacher's final season in F1 saw him finish 13th in the driver standings as fellow German Sebastian Vettel made it a hat-trick of titles in his Red Bull.

It was a far cry from his glory days at Ferrari where he won five titles and his two earlier championship successes with Benetton.

The 82-year-old Ecclestone has also faced calls to step aside from his role at the helm of F1, but said he would only quit when he felt he was not doing a good job.

"I hope that's what I can do: when I feel I can't deliver, I will certainly say goodbye," he said.

Highlighting the success of F1's return to the United States at Austin, which he said was "perfectly prepared, Ecclestone added that everything about the sport was "super positive" and hinted at further expansion plans, which will see Russia added to the grand prix calendar.