"He's extremely knowledgeable," Gailey told the Bills' official website. "He's a great human being. A great team guy, and he would bring some intensity to our team because I know what burns inside of him."
The Bills didn't provide details in telling The Associated Press that the meeting had taken place, but Gailey described what would happen on the visit.
"It's not me that he needs to meet with," Gailey said. "He's meeting with the defensive staff, which is the biggest meeting. He and I have known each other a long time, and I have a great deal of respect for Dave."
Forced to resign as the University of Pittsburgh's coach last month, Wannstedt has an extensive defensive background and would be a good fit for a Bills defense that had difficulty stopping the run this season and allowed 30 or more points nine times.
What's unclear is what position Wannstedt would be offered in Buffalo. The Bills currently have one opening, at inside linebackers coach, after DeMontie Cross was fired last week.
Gailey said told the team's website that there haven't yet been talks of specific duties should Wannstedt join the staff.
"I think he would be a very good fit, but it remains to be seen if this is something he would like to do or not," Gailey said. "So he'll have to think about it and see what direction he wants to go."
Despite the Bills' 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.
Buffalo's defense was last in the NFL against the run, allowing 2,714 rushing yards -- the second-highest total in franchise history. The Bills allowed 200 yards eight times.
Wannstedt was ousted after six years at Pittsburgh, following a 7-5 season in which the Panthers were picked to win the Big East Conference. He declined the option to finish the season with the team and wasn't on the sideline for Pitt's 27-10 victory over Kentucky in the BBVA Compass Bowl last weekend.
The Associated Press contributed to this report.