KANSAS CITY, Mo. -- Justin Herbert had just turned 10 years old when Chiefs quarterback Chad Henne was drafted by the Dolphins.
Think that's wild? The Chargers QB was still in high school the most recent time Henne started a game.
That makes quite the matchup Sunday when the 22-year-old Herbert, who has surpassed just about all expectations during his breakout rookie season, starts for the Chargers in Kansas City.
Opposite him will be the 35-year-old Henne, who takes over for Patrick Mahomes as the Chiefs (14-1) rest their starters with the No. 1 seed in the AFC playoffs already secured.
"I mean, it's the opportunity to go out there and be a starter in the NFL. You don't take it for granted," said Henne, whose previous start came on Sept. 21, 2014, when he was benched by the Jaguars in favor of rookie Blake Bortles.
"Play like you're 20," Henne added with a wry grin. "Go out there and be you."
Or at least like you're 22 -- Herbert won't turn 23 until March. Yet his first year with the Chargers (6-9) has been a success everywhere but the win-loss column, where they will once again miss the playoffs.
Since taking over for Tyrod Taylor for their Week 2 game against Kansas City, Herbert has thrown for 4,034 yards with 28 touchdowns, setting an NFL rookie record for TD passes in a season. He's also set a rookie record with seven 300-yard passing games, and he needs 340 yards passing against the Chiefs -- who figure to rest most of their starters -- to break Andrew Luck's rookie record of 4,374 yards set during the 2012 season.
"You blink and you realize you're in Week 17," Herbert said, "and it feels like it was just yesterday we played the Kansas City Chiefs. I just think it's gone by so fast; this season has gone by so fast. It seems like yesterday."
Just because the Chiefs are resting most of their starters, including quarterback Patrick Mahomes, and the Chargers are out of playoff contention, there is still plenty of reasons for both teams to put forward their best effort.
The Chiefs can match the 2011 Packers with the best record by a Super Bowl champion with a win, not to mention break the franchise record by winning their 11th consecutive game. They also would feel a lot better going into their coveted bye knowing they played well, given that they struggled mightily on offense in last week's win over Atlanta.
The Chargers, meanwhile, have won their past three games behind winning drives in the fourth quarter or overtime, and knocking off their biggest impediment to progress in the AFC West would cap a strong finish heading into the offseason.
"We've always had a good plan against these guys," said Chargers Coach Anthony Lynn, whose team took the Chiefs to overtime in Week 2. "They're a tough opponent. We've had some success against them when we haven't turned the ball over, but that's why they're the world champs. They have those guys that cause havoc."
