Nearly half of NFL head coaches could have Dec. 29, better known as Black Monday, circled on their calendars. The dreaded day after the regular season wraps up is when many NFL teams cut ties with their head coaches, whether it’s over a string of losing seasons, philosophical differences, salary negotiations going south or a poor rapport with players or the front office.

Whatever the reason, a massive head coaching vacuum could be switched on for as many as 13 teams this offseason. That’s a substantial number, considering only five coaches were fired on Black Monday last season, which was slightly down from the six that were let go in 2012.

It’s highly unlikely that all 13 coaches listed below will be fired, but most have been linked to the hot seat this season for a plethora of reasons. Four, however, could save their jobs by making the postseason.

And it’s not like owners have a huge pool of worthy candidates to replace whomever they fire. There are only a handful of coaches in the college ranks (Alabama’s Nick Saban, UCLA’s Jim Mora, Oregon’s Mark Helfrich), who could in theory either return or make the jump to the NFL.

Many of the coaches listed here were NFL coordinators in their first stints as head coaches, and overall things have not panned out well. There are many current NFL coordinators who could garner significant interest, but most are unproven as head coaches, so teams might hesitate to fire a coach for at least another year.

Below are the 13 coaches who are possibly on the hot seat. Included is a summary and their overall record with their respective teams.

Ken Whisenhunt, Tennessee Titans (2-12)

Whisenhunt has a poor track record with quarterbacks. Due to injuries and perhaps personality clashes, he went through a number of starters when he was with Arizona, with only Kurt Warner working out to reach the Super Bowl. In his first season with Tennessee, Whisenhunt’s dealt with injuries to Jake Locker and Zach Mettenberger, and now veteran Charlie Whitehurst will take over against Jacksonville Thursday.

Because it’s his first year, and with the 2-12 Titans likely possessing a top three pick in next year’s draft, Whisenhunt could go out and pick his quarterback of the future and start from scratch next season. His seat is likely warm, but not burning up until next year or the year after.

Gus Bradley, Jacksonville Jaguars (6-24)

About to complete his second straight season with at least 12 losses, Bradley got his quarterback of the future in Blake Bortles with the No. 3 overall pick and it’s been a disastrous start for the Jags. The offensive line hasn’t protected the rookie at all, letting up a league-worst 62 sacks, and the running back and receiver positions have been decimated by injuries all season. Consequently, the Jags are worst in the league with 15.1 points per game, but the defense, which also dealt with injuries to top defensive back Jonathan Cyprien and linebacker Paul Posluszny, at times showed major flashes of improvement.

Defense was how Bradley got the job in 2013, helping mold Seattle’s young players into the group that’s threatening to repeat as Super Bowl champs. Bradley likely gets another year, but how Bortles plays next season will be a huge factor.

Jay Gruden, Washington Redskins (3-11)

His perceived and reportedly ongoing feud with quarterback Robert Griffin has plagued the Redskins and Gruden’s first year with the squad all season. Now it seems owner Daniel Snyder is in a “it’s him or me” situation with both his head coach and the player he sacrificed three first-round picks to obtain. Gruden went so far as to suggest that no matter what he says about Griffin, his words get “twisted” and the fire just continues to burn.

Nevertheless, similar to Bradley, Gruden was brought in to specifically help the Redskins offense like he did the Bengals. Washington signed receiver DeSean Jackson to give Griffin and Gruden a deep threat, and running back Alfred Morris is one of the more underrated players at his position, gaining 948 yards and seven touchdowns and likely en route to his third straight 1,000 yard season since entering the league.

But the Redskins are 26th in the league with 18.4 points per game, scoring less than 20 points in eight games this season. That stat could ultimately decide Gruden’s fate.

Jim Harbaugh, San Francisco 49ers (43-18)

The most talked about and likely gone coach on this list is Harbaugh. He led the 49ers to three straight NFC title games and nearly won a Super Bowl, but the reportedly strained relationship with general manager Trent Baalke means Harbaugh should be gone. He could have saved his job with a deep run in the postseason, but San Francisco’s 1-4 NFC West record blocked off that chance.

Firing him outright, though, might seem too rash. The Raiders and Jets reportedly both showed interest in a trade for Harbaugh, so the 49ers could at least get draft picks in return for a coach that has one year and $5 million remaining on his contract. Harbaugh can also bolt for the Michigan job.

Joe Philbin, Miami Dolphins (22-24)

At 7-7, the Dolphins need to win out and need some serious help from other teams to earn a wild-card berth. In all likelihood, Miami will miss the playoffs for the sixth straight year, and a Miami Herald columnist said team owner Stephen Ross came out of the Dolphins locker room after Sunday’s 41-13 loss to New England looking “sullen” and in a “foul mood.”

To his credit, Philbin seems to have done a solid job with third-year quarterback Ryan Tannehill and the Dolphins were seriously challenging for the playoffs before losing three of their last four games. Miami’s defense has also played very well in stretches this year, all of which could save Philbin. Last year's bullying scandal involving Jonathan Martin and Richie Incognito didn't help his job security.

Marc Trestman, Chicago Bears (13-17)

According to reports, Trestman’s fate has already been decided after a disastrous year. The Bears will miss the playoffs for the fourth straight year, and despite considerable talent at the skill positions they are 18th in total offense and 19th in points per game for a coach that made his mark with offense in the CFL.

Trestman is also losing control of the locker room, with two players questioning how he doles out discipline, ESPN Chicago reported Thursday.

Mike Smith, Atlanta Falcons (65-45)

Poor clock management and late-game strategies have plagued Smith all season, and he could be out of a job after narrowly avoiding the axe after last season’s 4-12 run. Smith’s put together a solid seven-year run with Atlanta, but he’s 9-21 the last two years after making the postseason in four of his first five years.

Jason La Canfora of CBS Sports reported last month that Smith is not expected back next season, but there is an outside of chance of Atlanta making a push in the postseason. Unless they do, Smith is likely gone.

Rex Ryan Jets 2014 Rex Ryan's in the midst of his second losing season with the Jets, and he could be gone on Black Monday. Photo: Reuters

Rex Ryan, New York Jets (45-49)

Perhaps no other coach faces as much scrutiny as Ryan on a week-to-week basis, though he’s in the midst of only his second losing season since he became the Jets head coach in 2009.

The Jets defense is still one of the more talented and productive in the league, ranking fourth against the run and sixth in total defense. But his failure to develop quarterbacks Mark Sanchez and now Geno Smith, and missing the postseason for a fourth straight year, signal that Ryan is on his way out.

Tom Coughlin, New York Giants (95-79)

Coughlin is on the verge of back-to-back losing seasons, his first such run as Giants head coach, and when the same occurred in Jacksonville in 2002 he was shown the door. At age 68, it's also unclear how long Coughlin wants to coach.

New York could finish 7-9, but making the playoff is obviously out of the question. The team struggled with injuries along the offensive line, and were without star wide receiver Victor Cruz for much of the season, adding to the offense's woes. Speculation has been rampant all season of the Giants and Coughlin parting ways, but New York might be better off retaining Coughlin than paying a premium for the likes of Bill Cowher or Jon Gruden, both of whom have been linked to New York in the past.

Tony Sparano, Oakland Raiders (2-8)

Sparano technically can’t be fired as head coach, since he was dubbed Dennis Allen’s interim replacement back in September. His 2-8 record since taking over doesn’t help Sparano’s chances of earning the full-time position, but he got a ringing endorsement from quarterback Derek Carr, who told the Bay Area News Group that he and the rest of the team “love” Sparano.

Having the support of your players certainly helps, but Sparano owns a 31-44 all-time record as a head coach and has made the postseason just once.

Jason Garrett, Dallas Cowboys (39-31)

Garrett’s contract expires at the end of the season, and it’s a topic that has floated around the Cowboys for quite some time. The team, especially the defense, has played well above expectations and is in line for the NFC East title if they can win out or just beat out Philadelphia. Still, just making the postseason might not be enough for Garrett.

He’s never made the playoffs as Cowboys head coach, and posted three straight 8-8 seasons before this year. Team owner Jerry Jones has also been mum on any talk of an extension. Making the playoffs and winning at least one postseason game likely earns Garrett a new contract.

Ron Rivera, Carolina Panthers (30-32)

Following up a 12-4 year with a 5-9 showing certainly hurts the fourth-year coach, but the Panthers can still make the playoffs by winning the NFC South. To his credit, Rivera molded the Carolina defense into a fierce crew last season, and this year they sorely missed top defensive end Greg Hardy.

Quarterback Cam Newton, though, hasn’t really improved year-over-year under Rivera, the only NFL coach he’s known. The 2014 season marks Newton’s worst, posting a 81.8 passer rating and throwing just 16 touchdowns. Again, making the postseason likely gives Rivera another season, and maybe another after that.

Sean Payton, New Orleans Saints (79-47)

Considering how the team stood by him during Bounty Gate, it would seem like very outside-the-box thinking for New Orleans to even contemplate ousting Payton, the only coach to help the franchise win a Super Bowl. However, the Washington Post added Payton to a list of coaches who “are sure to pop up on the chopping block.”

The Saints are currently first in the NFC South, and if they win out they’re in the postseason, where they could make some noise. Omitting his suspended 2012 season, Payton has taken the Saints to the postseason four straight times, and five overall since he took over in 2006.

It seems more likely that New Orleans fires defensive coordinator Rob Ryan, who reportedly isn’t getting along with Payton, according to CBS Sports.