Begin with Chiefs quarterback Patrick Mahomes, who started his first NFL game against the Broncos to close out the 2017 regular season and has since started two Super Bowls, won a league MVP, a Super Bowl MVP and is three weeks from his 26th birthday. Add coach Andy Reid and wide receiver Tyreek Hill to a list that also includes ill-timed Broncos' turnovers and Chiefs' touchdown returns.
But amidst that list, likely nudging his way near the top, is tight end Travis Kelce, who has vexed, exasperated and overwhelmed a growing assortment of Broncos defensive coaches.
While nobody will say it out loud as the Broncos' preseason rolls into its final week, Kelce is one of the reasons the Broncos have been so intent on getting rookie cornerback Pat Surtain II out of Alabama ready for regular season.
"I mean just his athletic ability," said Broncos safety Justin Simmons. "As long as we get him lined up in the right spot against the man he has to be on or the zone concept that we have implemented for that game plan he's going to be great."
"We're fortunate we have a player in Surtain that can play multiple positions at a young age," Broncos general manager George Paton said. "Not many rookies can play three positions. It's a really good problem to have ... you can't have enough of those guys."
There is plenty of water to flow under the football bridge before the Broncos have to worry about the Chiefs -- the two don't play the first of their two meetings until Dec. 5 in Kansas City -- and Surtain will have plenty to do between now and then.
But Kelce represents, as the most consistent irritant to the Broncos, the bigger picture problem Denver's defense has had over much of the past five seasons, when opposing tight ends have racked up 22 touchdowns and seven 100-yard games.
Kelce has faced the Broncos in 10 of Kansas City's 11 consecutive wins, including five 100-yard games. The Broncos don't face another player who has 100 yards in 50% of the games against them.
In the 10 games, Kelce has 73 catches for 930 yards and five TDs, numbers that would be a potential Pro Bowl season at the position in almost any year.
"The difference with Kelce is not only do you deal with what he can do, but he's got a quarterback like Mahomes getting him the ball, your margin for error is a lot smaller, that's a whole other deal," Broncos Hall of Fame cornerback Champ Bailey said.
Offensive coordinators love the impact of a physical tight end who can move with uncommon agility. Essentially they're too strong to be covered by cornerbacks and too fast for the more physical safeties and linebackers. It's why Surtain is so important to this defense.
There was a time when the Broncos found themselves facing tight ends Antonio Gates and Tony Gonzalez twice a season and would use Bailey to cover them. Surtain is next in line.
"He's big, moves well, can run, looks like a safety, runs like a corner," said Bailey of Surtain. "I loved covering [tight ends], because I knew they couldn't run by me, so the deal is you have to be patient, keep yourself in position, don't get tangled up with them, but I knew if I stayed close enough I would get my hand on the ball."
The Broncos believed Surtain had the potential for rare versatility when they made him the ninth pick overall in this past April's draft. They knew he was mature, had been coached well and had the size and speed that are coveted at the position.
But Surtain's ability to take the information the coaches piled on him and, with the help of his veteran teammates, take it to the field, has accelerated the Broncos' willingness to add items to his to-do list.
He has worked at an outside corner position, worked in the slot as part of the nickel (five defensive backs) and worked as a weakside linebacker in the dime (six defensive backs) in addition to more traditional roles in those situational looks.
"He's a good size guy," Broncos linebacker Josey Jewell said. "He can move, and you guys saw it during the Vikings game. He moves well and he understands the game. It's been fun to play alongside him ... as the [middle linebacker] when he's out in dime. [I'm] talking to him pre-snap and showing him what we're going to get, definitely fun to watch a young guy like that who picks it up so fast."
In the Broncos' preseason opener, Surtain gave a rather tidy glimpse of how he could fit in a secondary filled to the brim with veteran talent. In a 33-6 Broncos' win, the two passes thrown Surtain's way by the Vikings were knocked down and intercepted for a touchdown.
What it can all mean by the time the Broncos face the Chiefs Dec. 5 and Jan. 9 remains to be seen with the likes of Darren Waller, Mark Andrews, Dallas Goedert, Logan Thomas and T.J. Hockenson among the tight ends on the Broncos' schedule before they would even get their first crack at Kelce.
Surtain won't just cover tight ends, but in a matchup league, his potential against best at that position is something to keep an eye on.
"You always like choices," Broncos coach Vic Fangio said. "Any time on defense you like to be able to do multiple things. We'll see what we can do."