KANSAS CITY, Mo. -- Kansas City Chiefs quarterback Patrick Mahomes is having a sizzling September heading into Sunday’s game at the Indianapolis Colts (1 p.m. ET, CBS). He has seven touchdown passes, which is tied for the league lead. He has yet to throw an interception. And his Total QBR of 82.4 is third in the NFL.

Chiefs coach Andy Reid said the way Mahomes makes football a priority even during a busy offseason can help explain why he's starting the season strong. Backup quarterback Shane Buechele said it's his physical training regimen, which is aimed at being ready at the precise moment that training camp begins. Mahomes chalks it up to the way Reid pushes him at training camp.

Regardless of the reason, it's just another September for Mahomes in his fifth season as the Chiefs' starter. His fast starts have come to be expected, but how does he stack up all time in the opening month? Is he the greatest September quarterback ever? The numbers make a pretty good case.

Mahomes' career September QBR of 86.7 is the league's highest since the statistic was first recorded in 2006. Peyton Manning is second on the list at 78.6, more than eight points behind. Mahomes' average of 322.6 passing yards per game is 27.2 more than anyone else in the month since at least 1970 (min. 10 such games), per ESPN Stats & Information.

The résumé continues. His completion percentage (68.8%) is the best among QBs with at least 500 career attempts in the first month of the season. Perhaps most convincing is his 48-3 touchdown-to-interception differential, giving him 16 September TD passes for every interception. That is far better than the next quarterback on the list there, Aaron Rodgers at 4.4-1.

It translates to team success too. Kansas City has gone 13-2 in September when Mahomes starts for a 86.7 winning percentage -- also the best for that month. Roger Staubach is second among quarterbacks with at least 15 September starts at 22-4 (84.6%).

All of which makes the case for Mahomes as the best September quarterback ever, not that he has been unproductive the rest of the season.

"I think he does pretty good all the time," Reid said.

Indeed, the Chiefs are even better in December, going 17-2 with Mahomes as their starter. That’s the best month ever record-wise for a starting quarterback in NFL history. But statistically, he’s at his best in September.

Luck can factor into it. In last Thursday night’s game, the Los Angeles Chargers could have intercepted Mahomes four times. Defensive back Asante Samuel Jr. dropped two picks. A third was overturned after a video review, and a fourth was nullified by a penalty, leading Mahomes to joke afterward, "I must be living right."

Otherwise, Mahomes has generally been on point in September. To Reid, his early-season success starts in the offseason, when Mahomes sets aside plenty of time for football despite a schedule also crammed with commercial shoots, trips to sporting events and family time.

"Football is important [to Mahomes]," Reid said. "I think if you ask him, family and football are right at the top of the list there among the things that he does. And so he's always going to do that whether he is doing a commercial or something. He is going to put that in the front, and it's not going disrupt what he's doing."

Mahomes rarely misses an offseason practice. This year, he organized some throwing sessions in the spring involving Chiefs receivers near his offseason home in Texas, a particularly important exercise after the team turned over much of its pass-catching group.

He’s tuned in to what Reid and offensive coordinator Eric Bieniemy want from him right from the start of a season.

"There are times in games where I know what play is going to get called before it gets called," Mahomes said. "We're so much on the same page. So when [Bieniemy] starts calling the play, I'm like, 'Yep, that's what I expected to get called.'"

Tight end Travis Kelce said he was initially apprehensive about how powerful the Chiefs' passing game would be after they traded receiver Tyreek Hill to the Miami Dolphins in the offseason. Hill is one of the most explosive players in the league and was the Chiefs’ leading wide receiver in each of the past six seasons.

Then Kelce went to Texas in the spring and participated in the Mahomes-led workouts.

"When I saw that going down, I knew guys were going to work their tails off and then we were going to be just fine," Kelce said.

Mahomes' 8.7 yards per attempt in September also is the NFL's best since at least 1970 (min. 300 attempts), and while his 2022 average is slightly lower at 8.0 without Hill downfield, it still ranks No. 5 in the league.

Chiefs’ training camp practices under Reid tend to be efficient. They don’t practice against other teams. Fights between players on the field are rare.

Fast starts once the regular season begins usually follow, even before Mahomes became the starter in 2018. The Chiefs started 9-0 in 2013, Reid’s first season. Then they were either 4-0 or 5-0 in each season between 2017 and 2020.

Mahomes said that’s not coincidence.

"I think it's how we do training camp," Mahomes said. "It's hard. I mean it's hard for everybody, but I think it prepares you to be ready Week 1. Then you go out there and just execute. Coach has a great game plan in, you have guys flying around that are ready to go, ready to play a game and not be at practice against each other.

"We get a lot of reps in training camp. We go up against a really good defense with a good scheme. Then coach Reid puts us in a lot of game-like situations, where we're having to run a two-minute drill or we're having to drive down the field on a long-drive drill and all these different situations, so that whenever we get to the game, you're not surprised by stuff."

Buechele is also from Texas and worked out with Mahomes during the offseason. He said he saw Mahomes taper his workout routine to be in optimal condition when he needed to be the most.

He also said Mahomes’ communication with Reid is most helpful early in a season, when some teams are still trying to figure which plays in their book might work and which ones don’t.

"They just think the same," Buechele said. "Once you're with each other for so long, you kind of think like, 'Oh, it's third-and-7, this is what we like here.' They've talked about that all during the week, situational things, and so they're always on the same page, which is huge to having success on the offensive side."

A big September from Mahomes this season might never have been more important to the Chiefs, who watched their AFC West rivals load up in the offseason. Mahomes answered by throwing for 360 yards and five touchdown passes in a season-opening win against the Arizona Cardinals. He then had a pair of TD throws in last week's win over the Chargers, a result that gave the Chiefs early supremacy in their division.

It's no surprise. It's always what they get from their quarterback, at least this time of the season.