KANSAS CITY, Mo. (AP) — The Kansas City Chiefs were already facing a formidable series of hurdles if they were going to qualify for the playoffs. On Friday, their road became even more daunting.
The Chiefs announced that quarterback Alex Smith had a small laceration of his spleen and would miss their pivotal game against the playoff-contending San Diego Chargers. That leaves career backup Chase Daniel to make his second career NFL start at Arrowhead Stadium.
"There's nothing you have to do any different," Chiefs coach Andy Reid said. "Chase has a good grasp of things. He's a smart guy, studies like crazy in case something like this happens."
The Chiefs (8-7) were playoff shoo-ins about a month ago, when they were 7-3 and eyeing the Broncos atop the AFC West. A first-round bye seemed a better bet than missing the playoffs.
Since then, they've won just once in five games. Now, they not only need to beat San Diego for the second time this season, then hope Houston falls to Jacksonville and Baltimore to Cleveland in a pair of games that will transpire at the exact same time.
Of course, the Chiefs can only control one thing: their game against the Chargers.
"We have to win to even have a shot," Daniel said.
Matter of fact, so does San Diego.
After snapping a two-game slide with an overtime win over San Francisco last weekend, San Diego (9-6) knows that a victory against the Chiefs in the final week of the regular season will qualify them for the playoffs for the second straight year.
"That's what everybody works for all year long, to have an opportunity to advance," Chargers coach Mike McCoy said. "It's a big division game. We're very familiar with each other."
The Chargers beat the Chiefs in overtime in last year's regular-season finale to squeak into the playoffs. And if that wasn't coincidence enough, the Chiefs had already locked up their playoff seed that day, so they rested their starters and Daniel got the nod at quarterback.
He'll have a bit more on the line this time around.
"We have a sharp game plan this week," Daniel said after his only practice with the first-team offense, "and it was great to get out here Friday and go over the entire game plan."
All of the similarities to last season hit home for Chargers quarterback Philip Rivers, who threw for 229 yards and three touchdowns in that game last December. But he also pointed out that it's a new year, and the Chiefs have a whole lot more riding on this one.
"The situation's different for them," Rivers said, "but we had to beat them to get in and here we are again, we have to beat Kansas City to get in. It's a team we know well, they know us well."
The playoff fates of both teams will be the predominant story line Sunday, but there are a handful of intriguing subplots. Here are some other things to remember:
MORE ON SMITH: Smith believes his spleen was hurt in the third quarter of last week's loss in Pittsburgh. At first, he thought he was dealing with indigestion. Smith will not need surgery but could be out six weeks, which means Kansas City probably needs to reach the Super Bowl for him to return this season. "It's obviously a very strange thing to be dealing with," he said.
GATES IN THE END ZONE:
 Chargers tight end Antonio Gates needs one touchdown reception to become the ninth player in NFL history with 100. He has 93 catches for 1,167 yards and 15 scores in 19 career games against Kansas City, the most TDs he's scored against any opponent.
HOUSTON'S PURSUIT:
Chiefs linebacker Justin Houston has a league-leading 18 sacks, two shy of the single-season franchise record set by Derrick Thomas in 1990. He brought down Rivers once when the teams met in October. "You have to account for him," Chargers coach Mike McCoy said.
B-FLO IS BACK:
Chargers cornerback Brandon Flowers, who was cut in a cost-saving move last offseason, will return to Arrowhead Stadium for the first time. Flowers spent the first six years of his career with the Chiefs, going to the Pro Bowl last year. "I loved every second of Kansas City. That's where I thought I was going to spend the rest of my career," he said. "I'm in San Diego now and I love every second of being over here."
RIVERS RUNS THROUGH IT:
Rivers needs three touchdown passes to match his career high set in 2008. He also needs 5 yards passing for his sixth career 4,000-yard season. "He's really good," Chiefs defensive tackle Dontari Poe said. "Gets the ball out of his hands really well."