"There's a lot to fix," O'Brien told reporters after the 34-20 defeat. "We have a long way to go here obviously. We had trouble stopping the run. Our defense could not get off the field, so we got down. We have to improve very quickly this week."
The numbers from the game don't tell the whole story. The Chiefs only won the yardage battle by a handful of yards, 369-360, and opened their title defense with a two-score win.
K.C. was far more dominant than that may suggest, though. It led 31-7 early in the fourth quarter before Houston's offense, which looked out of sync for a majority of the contest, scored a couple of late touchdowns to make it appear like a competitive game.
Texans defensive end J.J. Watt agreed with his coach's assessment of the loss:
"We didn't play well enough to win. We have to stop the run a lot better. We have to put ourselves in better situations on third down to get off the field. We have to create takeaways. We didn't do that.
"Tackling is the one thing that most teams haven't been able to do at a true high-speed level, as you'd like to do. It's one of the tougher things to do without putting your guys at risk. It's something we're going to get better at."
Chiefs quarterback Patrick Mahomes completed 24 of his 32 throws for 211 yards with three touchdowns and no interceptions. Kansas City's rushing attack averaged 4.9 yards per carry, highlighted by a breakout 138-yard night for rookie Clyde Edwards-Helaire.
Meanwhile, the Texans offense was forced to go pass-heavy while playing from behind, and quarterback Deshaun Watson was under constant pressure amid a lackluster performance from his offensive line.
Houston, which reached the divisional round of last season's playoffs before blowing a 24-0 lead in a 51-31 loss to K.C., has the talent to make some noise again this year. Thursday's loss showed there's still a sizable gap between the Texans and the Chiefs in the race for the AFC title, though.
O'Brien and Co. have some extra time to correct the mistakes before they face the Baltimore Ravens, another of the conference's chief championship contenders, in Week 2 on Sept. 20.