Harbaugh has one year remaining on the five-year, $25 million deal he signed in 2011.
Glazer also reports that Michigan has "reached out to 49ers" about the coach, and the Chicago Bears "could also show interest" if Harbaugh wants to stay in the NFL.
On Dec. 17, Michigan reportedly offered Harbaugh a six-year, $48 million contract.
The 49ers (7-8) play the Arizona Cardinals next Sunday. The team had played in three straight NFC championship games, including an appearance in Super Bowl XLVII in 2013. This season, San Francisco was eliminated from the playoffs on Dec. 14.
Harbaugh was the head coach at Stanford before taking over for the 49ers, and led the Cardinal to an Orange Bowl victory in his final season.
- Sarah Barshop