Sandro Wagner knows he's backup to Robert Lewandowski - Jupp Heynckes

Bayern Munich boss Jupp Heynckes has said new signing Sandro Wagner is aware that he will only be a backup for Robert Lewandowski.

Wagner, 30, returned to his boyhood club Bayern this month in a €12 million transfer from Hoffenheim.

The Germany international is set to add depth to the German champions' attack but, for now, will have to settle for a backup role.

"He's a player who has made a very positive development in recent years and become a national team player," Heynckes, who will be in charge until the end of the season, told reporters as the Bundesliga club departed for their winter training camp in Qatar on Tuesday.

"I think that he can help us."

However, Wagner, who returns to Bayern after stints with Duisburg, Bremen, Kaiserslautern, Hertha Berlin, Darmstadt and Hoffenheim, will not immediately be a starter at the Allianz Arena.

"I think that he knows about his role and is aware that a world-class attacker like Robert Lewandowski is ahead of him," Heynckes said, adding that the transfer carried "no risk" for Bayern either from a sporting and economical side.

The winter training camp in Qatar might be the last Bayern preparation for veteran winger duo Arjen Robben, 33, and Franck Ribery, 34, who are both under contract until the end of the season.

Contract talks have yet to be held, but former France international Ribery vowed to give it his all in the second half of the Bundesliga season.

"I will continue to work hard in 2018, and give it my all for club and fans," Ribery told German tabloid Bild.

"We have a good chance in Champions League, are in really good form and always want to win everything: Bundesliga, cup and Champions League, but it's difficult in Europe.

"We now have two matches against Besiktas. I know Istanbul. It's not easy -- you meet with a lot of resistance."

Bayern go into the second half of the Bundesliga season with a 11-point lead on Schalke. They have also knocked holders Borussia Dortmund out of the cup, and are now only two matches away from the final in Berlin.

In the Champions League, they take on Besiktas in the round-of-16, and thus remain on course to, after 2013, win a second Treble under Jupp Heynckes.

"We should not think about this now," midfielder Javi Martinez told Sport Bild. "It's way too early. It's now about having a good preparation for the second half of the season in Doha, and about maintaining the good form we so far have shown under Jupp Heynckes."