Chargers offensive coordinator Ken Whisenhunt, left, congratulates Philip Rivers after Sunday’s 27-10 win over the Bengals. (Stephen Dunn/Getty Images)

Redskins general manager Bruce Allen continues to widen his coaching search, requesting permission to interview San Francisco 49ers offensive coordinator Greg Roman and San Diego Chargers offensive coordinator Ken Whisenhunt, two people with knowledge of the situation said.

Under league rules, today represented the first day that either candidate was eligible to interview with prospective teams, because their teams both played in the opening round of the playoffs. Neither can be hired until their team is eliminated from the postseason, however.

Roman, 41, is in his third season with the 49ers and spent 2009 and 2010 with Jim Harbaugh at Stanford, serving as offensive coordinator there as well.

San Francisco 49ers offensive coordinator Greg Roman has drawn interest from the Redskins. (Getty Images) San Francisco 49ers offensive coordinator Greg Roman has drawn interest from the Redskins. (Getty Images)

Roman has emerged as a head-coaching candidate because of his success with a unit led by third-year quarterback Colin Kaepernick, running back Frank Gore and tight end Vernon Davis.

It wasn’t immediately clear if the 49ers would grant Washington permission to interview with Roman. The Minnesota Vikings also reportedly have requested permission to interview Roman.

Whisenhunt, 51, joined the Chargers this season after six seasons as head coach of the Arizona Cardinals. He guided the Cardinals to their first Super Bowl appearance in 2008, but they fell to the Pittsburgh Steelers. Whisenhunt served as Pittsburgh’s offensive coordinator from 2004 to 2006, and played for the Redskins from 1989-90.

Roman, whose team defeated Green Bay in the wild-card round of the playoffs on Sunday, and Whisenhunt, who on the same day helped the Chargers defeat the Bengals, become the ninth and tenth candidates on the Redskins’ list.

Allen and other team officials already have interviewed Seattle offensive coordinator Darrell Bevell, Dallas special teams coach Rich Bisaccia, Carolina defensive coordinator Sean McDermott, Baltimore offensive coordinator Jim Caldwell, and on Monday were expected to host Giants defensive coordinator Perry Fewell. The team on Monday also requested permission to interview both Cincinnati offensive coordinator Jay Gruden and defensive coordinator Mike Zimmer, as well as Vanderbilt coach James Franklin.

Update, 3:55 p.m.:

The Redskins also have requested to interview San Francisco defensive coordinator Vic Fangio, a person with knowledge of the situation confirmed. Fangio has  14 years of experience as a defensive coordinator during stints with the Panthers, Colts, Texans and 49ers. His unit ranked fifth in the league this past season.

This brings the Redskins’ list of candidates to 11 coaches.

More from The Post:

Redskins interview Caldwell | Other candidates: McDermott | Bevell | Bisaccia

James Franklin expected to interview | All coaching search posts

Redskins interested in Jay Gruden, Zimmer | Jon Gruden, team haven’t spoken

Snyder still struggling to find winning formula | How desirable is the job?

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