Bayern are ten points clear at the top of the league and an away win at Mainz will guarantee the title with three games remaining.
Head coach Hansi Flick dropped a bombshell last weekend by saying he wants to be released from his contract at the end of the term and wants to sign off with the league title.
The Bavarians are boosted by the presence of Lewandowski, who has missed their last six games with a knee injury.
The Poland striker has netted 35 goals this season and is five short of Gerd Mueller’s all-time league record of 40 set in 1971/72.
“I don’t know if I’ll do it yet,” Lewandowski said on Wednesday.
“But I hope that when I’m back on the pitch, I can be at my usual level…
Keep on reading: Lewandowski back with Bayern on verge of ninth straight league title