WATCH: Patrick Mahomes shows frustration on sidelines as Chiefs get blown out 38-0 by Broncos

Patrick Mahomes had an off day when the Kansas City Chiefs faced the Denver Broncos in Week 18 on Sunday.

With the Chiefs entering the final week of the regular season with a 15-1 record, the team had nothing to play for. The first seed in the AFC was already locked, giving Kansas City a bye in the Wild Card Round and the home-field advantage in the conference. It was time to rest the starters.

Their opponent, however, had all to play for. The Denver Broncos needed to win the game to officially lock their playoff spot as the seventh seed in the AFC. Facing the Chiefs' backups, they earned a soundly 38-0 win.

Kansas City played almost no starters and the game meant nothing. But Patrick Mahomes was still left frustrated with the poor performance, especially as his team scored no points throughout the game:

In Mahomes' place, backup quarterback Carson Wentz, who won a Super Bowl with the Philadelphia Eagles, got the start. He had a dreadful afternoon, with just 10 completed passes and 98 yards.

Patrick Mahomes looking to make history with the Chiefs

Kansas City is looking to become the first NFL team in history to win three straight Super Bowls.

Mahomes finished the season with 3,928 passing yards, 26 touchdowns and 11 interceptions. He also had 307 rushing yards and two touchdowns in 16 games.

For most of the year, the Chiefs' offense had to deal with injuries. Rashee Rice was lost for the season in Week 4, Isiah Pacheco missed two months and, more notably, recent acquisition Marquise Brown lost almost all of the regular season with an injury. Pacheco and Brown have returned.

This was the first time since he became the starter that Mahomes passed for under 4,000 yards. However, he still led his team to an impressive campaign, with 15 wins in 16 games.

The Chiefs will play the Divisional Round at home, and if they advance, they'll also play the AFC Championship Game at home.