The Dallas Cowboys' season has once again come to a disappointing end. They lost on Sunday to the San Francisco 49ers, 23-17. The high-powered offense led by quarterback Dak Prescott was mostly held in check. But it was the mistakes committed by the Cowboys that were arguably the key reasons why they are going home early in the playoffs again.

There will be a lot of questions about how this happened. The season was supposed to be different for the Cowboys. They had a defense that led the NFL in takeaways. Their offense finished number one in points and yards per game. They cruised to an NFC East title and earned a home playoff game. Yet, here we are again, with the Cowboys losing in their first playoff game.

There is plenty to diagnose and fix for next season. One thing that must be done, the Cowboys need to fire head coach Mike McCarthy. Here are three reasons why.

*Watch NFL games LIVE with fuboTV (click for free trial)*

3 Reasons the Dallas Cowboys must fire Mike McCarthy

3. Cowboys lack of discipline

Seemingly every year, the Cowboys are eliminated either from the playoffs or from playoff contention because of self-inflicted wounds. This year was no different.

The Cowboys were flagged for 14 penalties against the 49ers. That tied the franchise record for most in a single playoff game.

The 14 penalties cost them 89 yards and appeared to come at the worst time. They either extended drives for San Francisco or came on a big offensive play, negating their big gain.

The Cowboys also did not seem prepared to start the game. The 49ers moved the ball at will on their first few possessions. Meanwhile, Dallas struggled to get any rhythm on offense. The team continued to try running Ezekiel Elliott, despite it looking clear to anyone watching football this year that Tony Pollard is the quicker, more explosive running back.

The Cowboys lacked preparedness and discipline. That falls squarely on the head coach.

2. Mike McCarty's resume is overrated

Yes, McCarthy is a Super Bowl-winning head coach. He captured the Lombardi Trophy with Aaron Rodgers and the Green Bay Packers in 2010. But many people would agree that that had much more to do with who was under center and less to do with McCarthy.

He coached in Green Bay from 2006 through 2018. Despite having a Hall of Fame quarterback every year, the Packers only made that single Super Bowl appearance.

McCarthy was frequently criticized for his lack of time management. That reared its ugly head up again on Sunday. With time winding down and the Cowboys out of timeouts, McCarthy did not object to offensive coordinator Kellen Moore's play call to have Prescott run a QB dive. 

Prescott rushed for more yards than he should have, and time expired before the Cowboys got another snap off. That inconceivable. The only thing you cannot allow to happen in that scenario is not even getting a shot at the end zone. Do you want a throw from the 25-yard line instead of the 40? Of course. Are you willing to gamble any shot at the end zone at all on a quarterback run? Not a chance.

Yet, after the game, McCarthy defended the play call (via NBC Sports).

“I've never seen that come down the way it came down as far as the collision between the umpire and the quarterback. We were trying to get inside the 30-yard-line to set up the last play. The mechanics were in-tact and I felt from our end of it, the communication I was given on the sideline was that they were reviewing it and they were going to put time back on the clock. The next thing I know they're running off the field.”

McCarthy, as the leader of the team, must make certain there is at least one throw into the end zone.

1. ‘Same Old Cowboys' need a fresh start

After a demoralizing loss, like the one they suffered on Sunday, a fresh start is a good idea.

In the 1990s, the Cowboys were the dominant franchise. They won three Super Bowls and were in the running seemingly every year. However, the last two decades have been tough on Cowboys fans.

America's Team has underperformed time after time. After a lackluster first season as head coach, McCarthy led the team to a 12-5 record and the NFC East title. This year was supposed to be different. Unlike in years past, the Cowboys defense had playmakers all over the field. Rookie linebacker Micah Parsons and second-year cornerback Trevon Diggs both had outstanding seasons. Both sides of the ball were filled with talent.

But once again, the season ended in a Wild Card playoff loss. A new voice in the locker room would not be a bad idea to help get over the defeat.