SANTA CLARA, Calif. - There could be an interesting twist to the San Francisco 49ers' search for a new head coach.

For the 49ers, who have been carried by their defense over the last four seasons, it would be logical to find a way to keep defensive coordinator Vic Fangio around while finding an offensive-minded head coach to improve that side of the ball.

But unless that coach is 62-year-old Mike Shanahan, the 49ers might not be able to do that, according to Mike Silver of the NFL Network.

I'm told word in coaching circles is 49ers DC Vic Fangio now wants out of SF unless he gets HC job... or Mike Shanahan does.

— Michael Silver (@MikeSilver) January 13, 2015

Shanahan, who last coached Washington from 2010 to 2013 after winning back-to-back Super Bowls with the Broncos in 1997 and 1998, interviewed with the 49ers Jan. 1, according to CSN Bay Area.

Fangio was one of the first candidates interviewed by San Francisco after parting with Jim Harbaugh. The 49ers reportedly blocked Fangio from interviewing for the open defensive coordinator job in Washington soon after the the regular season ended last month. The day after the final team's final regular season game against the Arizona Cardinals, defensive players spoke up about wanting Fangio to return as either a head coach or defensive coordinator. He has one year remaining on his contract he signed when joining the club in 2011 with Harbaugh.

The 49ers Tuesday interviewed Broncos offensive coordinator Adam Gase, 36, after Denver cut ties with head coach John Fox. Gase could also be a candidate to become the Broncos new head coach.

San Francisco has also been linked to Patriots offensive coordinator Josh McDaniels, but couldn't hire him until the end New England's season.

If Fangio was made head coach, he would reportedly prefer Shanahan's son Kyle to be his offensive coordinator. Kyle Shanahan has been linked to the New York Jets to become offensive coordinator under Dan Quinn, the Seahawks defensive coordinator, who is the favorite to become the Jets' head coach. The 49ers have also interviewed Quinn.

Gase is the first candidate to receive a second interview, which the 49ers cannot conduct with either Quinn or McDaniels until next week at the earliest after coaching in their respective conference title games.

Defensive line coach Jim Tomsula is still viewed as the favorite in-house candidate to replace Harbaugh, despite there being no known interview to this point.

Under Fangio, the 49ers defense finished fifth in the NFL in yardage in 2014 despite missing a number of key players for chunks of the season. Inside linebacker NaVorro Bowman was out for the year while recovering from ACL and MCL tears sustained last winter, while fellow linebacker Patrick Willis sat out the season's final 11 games by electing season-ending toe surgery. Fangio also fielded the league's fifth-ranked passing defense despite significant turnover in the secondary from the previous three seasons and a nine-game suspension for pass rusher Aldon Smith.

.more-stories {margin:20px 0;} .more-stories a{display:block;width:100%; background:#efb900;height: 52px;text-align:center;line-height:44px;color:#202020; text-decoration:none;text-transform:uppercase;font-family:bebas_neue;font-size:20px;position:relative;overflow:hidden;letter-spacing:2px;-webkit-transition:all .15s ease-in;transition:all .2s ease-in;border:3px solid #efb900;}.more-stories a:hover{color:#fff;background:0 0;letter-spacing:3px;background:#121212;border:3px solid #121212;} @media (max-width: 600px) { .more-stories a {height:auto !important;line-height:1.4em;padding:10px;} }

see what 49ers fans are saying here

Next story:

Report: 49ers seek second interview with Gase

[MEDIA:1463948]

E-mail Niners Digest: NinersDigest@gmail.com

Follow Editor-in-Chief Chris Biderman on Twitter.

Get updates from Niners Digest by following here and become a subscriber to receive access to premium content and analysis.