Wannstedt, who wants to become an assistant head coach, is in line for some type of coaching position on the Bills' staff, according to a league source.
Wannstedt is familiar with Chan Gailey, who completed his first year as the Bills' coach. When Wannstedt became coach of the Miami Dolphins in 2000, he hired Gailey as his offensive coordinator. Gailey spent two seasons with the Dolphins before moving on to coach at Georgia.
Wannstedt, who was forced to resign at Pitt last month, now appears ready to return to the NFL, where he was a Super Bowl-winning coordinator with the Cowboys and a head coach for the Chicago Bears and Miami Dolphins.
He has an extensive background as a defensive coach, and the Bills had trouble stopping the run in a 4-12 season.
Buffalo currently has a defensive opening at inside linebacker after DeMontie Cross was fired last week.
Despite Buffalo's defensive struggles, coordinator George Edwards is expected to keep his job after completing his first season. Edwards took the job less than a month after he was hired to be the defensive coordinator at the University of Florida.
The Bills' defense was last in the NFL against the run, allowing 2,714 yards rushing -- the second highest total in franchise history. Buffalo allowed 200 yards eight times last season.
Wannstedt was ousted after six years at Pittsburgh, and following a 7-5 season in which the Panthers were picked to win the Big East. He declined the option to finish the season with the team, and was not on the sideline for Pitt's 27-10 win over Kentucky in the Compass Bowl last weekend.
Adam Schefter is ESPN's NFL Insider. Information from The Associated Press was used in this report.