The 24-year-old, who joined Bayern in 2011, made just 12 appearances for the Bundesliga champions before being sent out on loan last June.
He has impressed while on loan at the German outfit with 11 goals in 29 appearances, a run of form that has reportedly won him a permanent transfer to Bremen.
"I am almost able to rule out Nils Petersen returning to Bayern. Joining Werder Bremen on loan was the right move for him. It's good for him to be at Werder Bremen," Coordes told reporters at a press conference.
"You just need to have a look at Bayern's squad. Mario Gomez is a substitute, Claudio Pizarro is also a substitute. I feel Nils Petersen does not need to be another substitute."
Bremen currently sit 14th in the Bundesliga table.