KANSAS CITY, Mo. (AP) -- Alex Smith thought he had some indigestion. It turned out to be a lacerated spleen.
Now, the Kansas City Chiefs will put their already slim playoff hopes in the hands of career backup Chase Daniel, who will make his second-ever start Sunday against San Diego.
The Chiefs need to beat the Chargers and hope that Baltimore loses to Cleveland and Houston gets beat by Jacksonville to reach the postseason for the second straight year. San Diego needs only to defeat its longtime AFC West rival to get back to the playoffs - and now faces a second-string quarterback.
"The guys have a lot of trust in Chase," Chiefs coach Andy Reid said shortly after Friday's practice. "Our heart goes out to Alex. It's not something he wanted to happen. He wanted to be out there. But the guys know Chase. They're comfortable with him."
Daniel should be comfortable facing the Chargers, too.
Last season, the Chiefs (8-7) had already locked up their playoff seed before their regular-season finale in San Diego. Reid rested his starters and Daniel made his first NFL start, playing well in an overtime loss that allowed the Chargers to squeak into the playoffs.
Smith is expected to miss about six weeks, Chiefs trainer Rick Burkholder said, though his age and fitness level could shorten that timeframe. The Chiefs would need to make the playoffs and then likely advance all the way to the Super Bowl for him to return this season.
"I didn't know what to make of it," Smith said. "Once you start hearing how serious it is, obviously yeah, you know the implications as far as not playing - that's the last thing you want to hear. At the same time, you're not crazy."
The Chiefs, who have lost four of five, have been plagued by injuries all season.
Defensive tackle Mike DeVito and linebacker Derrick Johnson were lost to torn Achilles tendons and offensive guard Jeff Allen a torn biceps in Week 1. Running backs Joe McKnight and Cyrus Gray, tight end Demetrius Harris and wide receiver A.J. Jenkins have joined them on injured reserve.
Then there's safety Eric Berry, who was placed on the non-football injury list and diagnosed with Hodgkin's lymphoma. Berry is currently undergoing chemotherapy and other treatments.
Smith believes he was hurt on a hit early in the third quarter of last Sunday's 20-12 loss at Pittsburgh. He didn't feel any pain until after he had showered, and then it felt like cramps and pressure. He visited with the team's medical staff but didn't go through full testing.
"Thought it was something I ate," said Smith, who ultimately took some antacids.
Smith practiced twice early in the week, feeling fine other than some nausea. There had been a stomach virus going around the team that kept wide receiver Dwayne Bowe from practicing all of last week, so Smith and the training staff suspected that might be the cause.
The Chiefs had off for Christmas and Smith didn't want to leave his family, but a team doctor helped persuade him to undergo a scan, which to his surprise found a 3-centimeter laceration. There was only a bit of bleeding, though, which explained why Smith had so few symptoms.
"If you would take another shot there and the laceration would increase, then you have a medical emergency," Burkholder said. "This is a 1-in-100 find for our doctors because he didn't have any signs of a spleen (injury)."
Burkholder said scans also revealed a slight enlargement of the spleen, and Smith will have more testing to determine why that's the case. Burkholder said it may just be natural.
"It's a non-surgical case. It will heal on its own, but he is going to have to have some time down from contacts and collisions," Burkholder said. "I won't go as far as to say that we saved a life, but you saved something that could go on Sunday."
Daniel, who starred nearby at Missouri, was acquired by the Chiefs last season. He's appeared in only seven games since, mostly in mop-up duty, but was 21 of 30 for 200 yards with a TD pass and no interceptions in that 27-24 loss to San Diego last year.
"We have a sharp game plan this week. We're excited about it," Daniel said after Friday's workout, "and it was great to get out here and go over the entire game plan."