Mayhew most recently spent eight seasons with the Detroit Lions as their general manager from 2008-15.
The 50-year-old was fired in November alongside Lions team president Tom Lewand after they started the season 1-7. He had previously interviewed with the Tennessee Titans during the offseason for the role of general manager, according to the Tennessean's Jason Wolf.
Per Eisen, Mayhew will work with assistant general manager Kevin Abrams on aspects such as player contract negotiations, salary cap issues and CBA compliance along with special assignments from general manager Jerry Reese.
The Giants were in search of a new member of their front office after Matt Harriss joined the Lions as their vice president of football administration, according to Eisen.
Mayhew is going to have his hands full with a Giants team that is going through some down times and changes.
New York's defense was dead last in the league, which is an uncharacteristic trait for a Giants organization that had always prized itself on that aspect of the game.
That will surely be something Mayhew, along with the rest of the front office, will have to help address in the coming months, whether it be through the draft or free agency.
After their 6-10 2015 campaign, head coach Tom Coughlin resigned after 12 seasons in New York and offensive coordinator Bob McAdoo was promoted to the position.
McAdoo, who instituted the West Coast offense with the Giants, has gotten some great years out of quarterback Eli Manning. Last year, the Giants offense was ranked eighth in the league in total offense in what proved to be a lone bright spot in a bleak season.
That alone frees up about $12 million in cap space for the Giants and Mayhew, who will try to build the Giants back up to a contender in the NFC. Bringing in a mind like Mayhew's, who has had general manager experiences with the Lions, can help the Giants make the right moves heading toward the 2016 season.
Stats courtesy of NFL.com