The manufacturer of the helmet that Kansas City Chiefs quarterback Patrick Mahomes shattered during his side's AFC wildcard game with Miami says it "did its job" by protecting the NFL's best player "during a head-to-head impact in unprecedented cold temperatures".

The game on Saturday was the fourth-coldest in NFL history, with the temperature at kickoff -20C, while winds gusting to more than 40km/h made the wind chill approach -34C during the game.

"Extreme conditions like those are bound to test the limits of even the highest-performing products," Certor Sports, which makes the helmet that Mahomes was wearing, said in a statement on Wednesday.

Mahomes was scrambling toward the end zone for the champions in the second half of the Chiefs' 26-7 victory when he was hit by Dolphins safety DeShon Elliott.

Their helmets clashed and, likely because of the extreme cold that made the outer shell brittle, a fist-sized chunk went flying from Mahomes' helmet just above the facemask covering his left eye.

"They're testing it right now," Mahomes said on Wednesday.

"But I'm adamant on getting the helmet after. It's something that's cool, I'll be able to keep for a long time. Like they said, it did its job. I was perfectly fine after."

Mahomes revealed he'd never previously had a helmet shatter on him - "It was a first for me," he said.

And he didn't know a shard had broken free until he returned to the huddle on Saturday night and teammates began pointing it out to him.

Mahomes initially played on with the broken helmet before officials intervened and made him get a backup from the sideline.

But the backup had been sitting in the extreme cold all night, and it was difficult for Mahomes to get on his head.

It took some work with equipment managers on the sideline between series to finally get it comfortable for him.

"We have to talk about where we store the backup because it was frozen," Mahomes said with a smile.

"It didn't look great. We were able to adjust it on the sideline, get it kind of warmed up a bit and get rolling from there."