The Indianapolis Colts (3-2) may have been massive underdogs on the road against the Kansas City Chiefs (4-1) on Sunday night, but that didn’t stop them from coming away with a 19-13 upset victory at Arrowhead Stadium.
Coming off of an embarrassing loss against the Oakland Raiders in Week 4, the Colts needed a bounce-back game Sunday night. They got that and more as they take a winning record into the bye week.
Here are four things we learned about the Colts in Week 5:

Marlon Mack is truly a three-down back
The offensive line certainly deserves their credit—more on that later—but Mack is truly coming into his own as a workhorse back. Despite all the question marks about having a heavy workload, Mack is taking his game to the next level.
On Sunday night, he torched the porous Chiefs run defense to the tune of 29 carries for 132 rushing yards. He was electric all night showing off improved vision, balance and patience behind the line of scrimmage.
The Colts are becoming a more balanced offense, and Mack is proving they can win games against the elite teams in the NFL.

The offensive line is still elite
Behind left guard Quenton Nelson and left tackle Anthony Castonzo, the Colts have arguably the best offensive line in the NFL. There were some struggles in Week 4, but the unit bounced back in a big way on the national stage against the Chiefs.
Not only did they pave the way for 180 rushing yards as a team, but they also didn’t allow a sack while only giving up three quarterback hits on Jacoby Brissett. The blueprint for the Colts’ success lives and dies with the offensive line.
The Colts know they have an elite starting unit up-front, and they will continue to control the line of scrimmage with the elite group of hog mollies.

The front seven showed up
Even without the benefit of having All-Pro linebacker Darius Leonard, the Colts managed to stifle the Chiefs potent offense. They held the Patrick Mahomes led unit to 13 points. It was the first time the Chiefs offense had been held to fewer than 26 points since Mahomes became the start.
A big reason for that was the relentless effort of the front seven. All across the defensive line, the Colts got consistent pressure. Justin Houston, Kemoko Turay, Grover Stewart and Jabaal Sheard were all involved on sacks while Bobby Okereke showed some improvements in pass coverage.
The Colts have to continue growing on the defensive side if the AFC South is going to be theirs, and the unit showed how high of a ceiling they can have when everything comes together.

Khari Willis is the real deal
The fourth-round pick out of Michigan State has emerged as a playmaker for the Colts in the backend of the defense. He might not have the range of Malik Hooker, but he is an extremely versatile piece that is developing quickly into a starter.
Willis has been solid in coverage for the most part since he’s taken over the starter’s role over the past three weeks, and he had one memorable pop at the line of scrimmage to stop Damien Williams on a run.
The Colts traded up 20 spots giving away two fourth-round picks to grab Willis, and it is becoming apparent why they did so.