It wasn’t supposed to happen.

Heading into Sunday night’s prime-time contest in Kansas City, the Colts were 11-point underdogs. They were 2–2 and coming off of a brutal 31–24 loss to the Raiders at home. They were preparing to face the best offense in the league without key defensive contributors and a secondary that was seriously shorthanded.

It didn’t matter. With a relentless effort up front and a stout showing from the team’s defensive unit, the Colts showed up and did what few predicted had them doing. They relied on Marlon Mack. They got to Patrick Mahomes. They accomplished Sunday night what they failed to do at Arrowhead in January.

They won, 19–13, and handed the Chiefs their first loss of the season.

Despite playing in the NFL’s current air-it-out era of football, Indianapolis decided to do something the majority of the league forgot existed: dominate the line of scrimmage. On offense, that meant using the big line to bruise a Kansas City defensive front that lost tackles Chris Jones and Xavier Williams to injuries. On defense, that meant finding ways to get Justin Houston into his old team’s backfield, plugging up holes in the running game and getting after Mahomes on every passing down.

It was old-school, grind-it-out football—and it worked. The holes on offense created space for Mack (132 yards on 29 carries) and plenty of time for Jacoby Brissett, who threw for 151 yards while running for the Colts’ only touchdown. The pressure on defense stifled the Chiefs despite a strong first two drives, during which Mahomes completed 13-of-17 passes for 157 yards and Kansas City’s lone touchdown of the game. He was held largely in check after that, getting sacked three times and holding the ball for just 22:45 compared to Indianapolis’s 37:15, resulting in the lowest scoring output of the reigning MVP’s career.

Adam Vinatieri took care of the rest, hitting three short field goals (32, 32 and 29) to keep the Colts ahead when points were scarce.

Yes, Mahomes was visibly unlike himself for three quarters of the contest. Hobbled by an ankle injury he re-aggravated in the second half, the league’s most dynamic young quarterback was noticeably less efficient—his 54.6% completion rate the second-lowest mark of his career. Kansas City’s offense is hopeless without him, and there’s no question the Chiefs could have been well on their way to 5–0 had Mahomes been the electrifying competitor we’ve seen since his very first start.

But that shouldn’t take away from what Frank Reich and the Colts achieved. Week 5 was highlighted as a marquee matchup before the start of the season, with Mahomes and then-starting quarterback Andrew Luck taking center stage. The 2019 season isn’t over yet, and Indianapolis’s remaining 11 games may not be any easier, but Reich can confidently rely on the fact that the Colts proved, even without Luck, that the roster is versatile enough to still be worthy of that kind of attention.

And if they continue to put on the type of performance they gave on Sunday, Reich can continue to believe they can still compete in all kinds of games. This team ready for any type of environment.

These Colts can make the wins happen.