There's a video a couple of years old floating around the internet that shows Patrick Mahomes, then the quarterback at Texas Tech, dropping to his knees and flinging a football 65 yards on a dare.

That answered any questions about his arm strength.

What wasn't answered during all those years with the Red Raiders was whether that rocket arm could deliver the ball consistently on point.

Yes, Mahomes threw far fewer interceptions than most folks recall, especially given the number of pass plays Texas Tech calls each game, but most cynics figured he would toss about as many picks as touchdown passes once he arrived in the NFL.

He answered that question last week against the Chargers, when he threw for 256 yards and four TDs without an interception in his first game as the Chiefs' full-time starting quarterback.

"He did a nice job, and now you have to back it up," Chiefs coach Andy Reid said Wednesday. "He understands that. He's wired that way. Plenty of room to improve and he knows it. He's working at it."

Such as sliding when he's under pressure, rather than taking a big hit. Mahomes absorbed far too many of those against the Chargers, and the Pittsburgh Steelers' ferocious defense no doubt is licking its chops at the thought of delivering another crunching blow on Sunday.

But when it comes to throwing passes into double coverage, or taking a gamble that results in a costly turnover, at least for one week Mahomes was perfect.

And it's hard to get much better than perfect.

"Good and bad, you lean from both of those. But he made some nice decisions," Reid said. "There's some things he can go back and look at and say, 'I should have gone there.' That's in the memory bank and he's building that file. I thought he did a good job of not throwing it to them, but there are some things he could do better against certain looks."

Reid wouldn't go into details, of course, lest he gives the Steelers any unnecessary advantage. But whether it was a quick-flip pass to Tyreek Hill that resulted in a long touchdown, or a touch throw down the sideline to Anthony Sherman for another score, Mahomes never put the ball in too much danger.

More than all those throws he made, it was the throws he didn't make in the 38-28 victory that helped Mahomes win this season's first AFC offensive player of the week award.

"It helped that I had a lot of guys that played well for us in the offense," Mahomes said. "Tyreek had a great game, the offensive line played really well. I'm glad I got the honor, but it was kind of an offensive unit honor."

It's hard to gauge the growth in Mahomes from last year to this year, given how little he played as a rookie. But offensive lineman Mitchell Schwartz said it's evident in all aspects of his game, whether it was the way Mahomes approached offseason workouts or the way he operates in the classroom.

"There's definitely a comfortability with everything," Schwartz said. "There's been a huge progression from him and it's been cool to see."

Just as Reid said, though, now Mahomes needs to back up his Week 1 performance.

The Steelers present a much more complex test for Mahomes with a variety of disguised blitzes that have frustrated Chiefs quarterbacks for years.

Even the cerebral Alex Smith, the consummate game-manager quarterback, struggled to have much success against Pittsburgh during his years in Kansas City.

"I feel like I get better and better with blitz protections every week. It helps that we have good game plans," Mahomes said. "I know Pittsburgh does a ton of that stuff, that's kind of their thing, but we've played them a lot the last few years, so we kind of know what to expect."

Notes: Eric Berry remained out of practice Wednesday. The team had described his injury as a heel issue in training camp, but Reid clarified that it is Berry's Achilles tendon causing issues. The star safety tore his Achilles tendon last season. "Just being cautious with it," Reid said. "We have full trust in him. He's always very honest with us. We want him there for the long haul. We're trying to make sure everything is right there." ... LB Ben Niemann (hamstring) also did not practice Wednesday.