Petersen made a €2.8million (2.4million) move to Bayern from Energie Cottbus in the summer of 2011 but has struggled to command a first team place.
The 24-year-old made just 12 appearances in his first season with the Bavarian giants and was sent out on loan to Bremen last June.
He has enjoyed much more success with Die Werderaner this campaign, with 11 goals in 29 appearances to far.
Despite still having two years left on his Bayern contract it appears unlikely he will return to the Allianz Arena at the end of the season.
Former Hamburg manager Coordes, who is a member of boss Jupp Henyckes' scouting team, believes Petersen would be better off signing a permanent deal at Bremen or risk sitting on the bench again at Bayern next season.
"I am almost able to rule out Nils Petersen returning to Bayern," said Coordes.
"Joining Werder Bremen on loan was the right move for him. It's good for him to be at Werder Bremen.
"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."