Reeves was a head coach for 23 seasons in the NFL with Denver, the Giants and Atlanta. But he has been out of coaching since being replaced by Wade Phillips with three games left in the 2003 season with the Falcons.
Reeves, 65, had a 190-165-2 record as a head coach, making the postseason nine times and losing in all four trips he made to the Super Bowl.
Reeves won the AP Coach of the Year award twice in his career, getting it for his work in 1993 with the Giants and '98 with Atlanta. He spent his first 12 years of coaching in Denver.
A phone message left at Reeves' Atlanta home wasn't immediately returned.
Earlier Friday, Baltimore Ravens quarterbacks coach Hue Jackson also interviewed for the open San Francisco coordinator job.
San Francisco's next offensive coordinator will be the team's seventh in seven seasons. The 49ers offered the job to Scott Linehan earlier this month, but the former St. Louis Rams coach turned it down and took the same job with the Detroit Lions on Friday.
Singletary has interviewed former Boston College coach Jeff Jagodzinski, Cleveland offensive coordinator Rob Chudzinski and Indianapolis receivers coach Clyde Christensen for the job. Denver assistant Rick Dennison also interviewed, but stayed on the Broncos' new coaching staff.