But Norbert Haug, German marque Mercedes' competition director, admitted to Bild am Sonntag newspaper that he can imagine teaming up with the famous 42-year-old in 2013 as well.
"If Michael wants it and we can agree on a right price — with pleasure," said Haug.
After fitting a late and major upgrade for the W02 car, Mercedes had a strong end to the 2011 pre-season period.
"Michael looks really strong," admitted team boss Ross Brawn. "He could surprise some people this year."
Before leaving Barcelona where the last winter test before the Australian season opener is held, Schumacher smiled as he admitted his best time was "not bad".
"On the favorites list, they are now climbing to the top," admitted Red Bull's reigning world champion Sebastian Vettel.
Referring to the final Barcelona test, former triple world champion and commentator Niki Lauda said: "It was a big step forward. The times were great."