* Wehrlein joins Sauber F1 team
* German was Mercedes reserve and Manor driver
* Move paves the way for Bottas to join Mercedes
* Bottas lined up as replacement for F1 champion Rosberg (Adds detail)
By Alan Baldwin
LONDON, Jan 16 (Reuters) - German driver Pascal Wehrlein will race for Sauber this season, the Swiss-based Formula One team said on Monday in a move that clears the way for Finland's Valtteri Bottas to join world champions Mercedes.
Wehrlein, 22, was the Mercedes reserve driver and raced for tail-enders Manor last year. He also won the DTM (German Touring Car) championship in 2015.
Mercedes need to replace Germany's world champion Nico Rosberg, who retired in December, and their choice was seen as being between their own young driver or signing the more experienced Bottas from Williams.
Wehrlein's hopes had already receded considerably, however, with Williams deputy team principal Claire Williams saying on Sunday that a deal for Bottas to move was almost done.
Confirmation of the Finn's future is expected imminently, with Brazilian Felipe Massa expected to come out of retirement and race again for Williams alongside Canadian teenage rookie Lance Stroll.
Instead of partnering triple world champion Lewis Hamilton at Mercedes, Wehrlein will now race for a Ferrari-powered team and take the place of Brazilian Felipe Nasr as team mate to Sweden's Marcus Ericsson.
"It is a new challenge in a new team, and I am really excited and looking forward to this new adventure. Our objective is to establish ourselves in the mid-field and to score points on a regular basis," Wehrlein said in a Sauber statement.
"I want to say a big thank you to Sauber for trusting in me and giving me this great chance. And surely, a huge thanks also goes to Mercedes for the support."
Sauber finished 10th overall last season, a place ahead of Manor - who have since gone into administration - thanks to points scored by Nasr in his home race. Wehrlein had scored Manor's only point in Austria.
"Pascal has shown his talent throughout his career, in single seater racing as well as in the DTM," said Sauber principal Monisha Kaltenborn.
"Last year in his rookie Formula One season, he proved his potential by scoring one point in the Austrian GP in Spielberg. There is surely more to come from Pascal, and we want to give him the chance to further grow and learn at the pinnacle of motorsport." (Editing by Ed Osmond)