Raiders coach Klint Kubiak proclaimed at halftime Las Vegas would beat the Chiefs. He forgot to tell Patrick Mahomes

Klint Kubiak tried to provide some bravado against Patrick Mahomes and the Kansas City Chiefs that the Las Vegas Raiders desperately need. The Raiders evidently still have a ways to go, even if they're closing the gap.

Kubiak was feeling good at halftime with the Raiders leading by three points, telling CBS' Tracy Wolfson, "We're gonna win the game."

That didn't happen. The Raiders gave the Chiefs everything they could handle, taking a lead deep into the fourth quarter. Kansas City came up with a big drive to take the lead, the Raiders fumbled a kickoff return, and that largely doused their upset hopes. The Chiefs won 30-27 but it was far from easy. The Chiefs-Raiders rivalry has been one-sided for a while, but perhaps that's changing.

"When there's two good teams, that helps the whole thing," Chiefs coach Andy Reid said, via Charles Goldman of A to Z Sports . "That was a battle. That's what this is all about. It's healthy."

The Chiefs are 4-0 and clearly back to being the favorite in the AFC West after a down season. Mahomes is back from a torn ACL and Kansas City still knows what it takes to win close games.

But the Raiders, now 3-1, showed they have made plenty of strides. The outcome against the Chiefs and Mahomes was familiar, but it doesn't seem like the same, old Raiders anymore. Las Vegas just isn't quite to the Chiefs' level yet, even if the Raiders' coach wants that process to be sped up a bit.

"You find out way more about yourself through adversity," Kubiak told the media afterward . "And so, we have some adversity right here."

The Raiders came into the game undefeated and were confident. On a well-designed play, Kirk Cousins started to roll right, stopped and threw back to tight end Ian Thomas for a 27-yard touchdown and a 7-0 lead.

The Chiefs weren't bothered by the Raiders hitting the first big play. They responded right after with a long drive and a Mahomes touchdown pass to Tyquan Thornton.

The Chiefs and Raiders traded field goals in the second quarter, and then Las Vegas rallied to get downfield and got a 48-yard field goal as the half expired. That gave them a 13-10 lead at halftime and Kubiak some confidence, as he told Wolfson the Raiders would win.

Maybe that bravado got the best of Kubiak early in the second half. The Raiders hit a field goal but there was an illegal formation penalty on the Chiefs. Instead of taking the points, the Raiders accepted the penalty and went for it on fourth-and-2. The Chiefs got pressure and forced an incompletion, and the score remained 13-10. The field goal that came off the board would matter later.

"We're going to be aggressive going into the game. I don't regret it," Kubiak said after the game, via Sam Gordon of the Las Vegas Review-Journal. "I regret not getting it."

Eventually the Chiefs would take advantage and take back the lead. They usually do.

Kenneth Walker has been a huge addition for the Chiefs and he made a big play to end the third quarter. Walker got free to the right side and broke a 76-yard run. He was brought down at the 8-yard line and Mahomes hit Thornton for a touchdown two plays later. That gave the Chiefs a 17-13 lead.

The Raiders couldn't land a big blow in the fourth quarter but got a couple of field goals to take a 19-17 lead with 4:53 left. To that point the Raiders had done a great job getting pressure on Mahomes and limiting Walker, aside from his long run. But the Chiefs thrive in situations like being down two points with less than five minutes to go.

They didn't waste much time. Mahomes floated a pass to Thornton, who brought it in for 55 yards. Thornton suffered a gruesome ankle injury on the play , further thinning out the Chiefs' receivers. Thornton had caught two touchdowns and another huge grab that put the Chiefs in field-goal position. Walker scored to give Kansas City the lead back with 3:21 to go. The 2-point conversion was unsuccessful but the Chiefs led 23-19.

Then the Raiders made the one mistake they couldn't afford. On the next kickoff return, Dareke Young had the ball punched out and the Chiefs recovered. Walker scored right after that and a four-point lead was suddenly 11.

The Raiders got a touchdown from Brock Bowers after that but couldn't recover an onside kick.

The Raiders did get a stop but the Chiefs downed a punt at the 1-yard line with 1:16 to go. A pass to Tre Tucker around midfield was dropped, but that wasn't spotted before the Raiders spiked the ball to stop the clock so the reception stood. The Chiefs got pressure on Cousins on the next play and intercepted him to clinch the win.

The Raiders played well enough that it made sense Kubiak felt they were about to win. He's a new head coach and new to the AFC West. Sunday was a lesson on not taking anything for granted against the Chiefs and Mahomes.