KANSAS CITY, Mo. -- Following his second week fighting a stomach ailment, defensive end Frank Clark played more against the Denver Broncos on Sunday than the Kansas City Chiefs initially anticipated.

Clark, who said he started the season around 260 pounds but at one point during his illness had dropped to 238, played more Sunday because he was feeling good. An injury to fellow defensive end Alex Okafor also played a part, as did Clark's insistence to get on the field.

"We started off [slowly] with him, but he gets very aggravated with that," Chiefs coach Andy Reid said. "So you're better off just letting him get in and go. I found that out the week before.

"The fact he played as well as he did [Sunday] amazed me. This kid loves to play the game. I know he wasn't feeling well all week, and then for him to come out there, I wasn't sure exactly how many snaps he was going to be able to play. But he was bound and determined to get out there."

Clark wouldn't go into specifics, but he did shed some light on his stomach situation.

"I had an appendectomy a few years ago, so there are a lot of complications from that if you know anything about appendectomies," he said. "My stomach is a little bit weaker, my immune system is a little bit weaker, so I've got to do a better job of fighting stuff off from my side."

Clark has begun to gain back the more than 20 pounds he said he lost because of the illness. He said he played Sunday at 245 pounds and would continue to replace the weight he lost.

"Week after week, I'm just going to keep on building until I get back to the point where I feel I need to be," Clark said.

Last week, he sought help from stomach specialists and spent a night in a Kansas City hospital before playing 46 snaps against the Broncos. Even though he didn't have a sack, he was still a factor, hitting Broncos quarterback Drew Lock twice.

Clark has proved stubborn when it comes to getting on the field, healthy or not. He also demanded more playing time in the previous game against the New England Patriots, his first since coming down with the stomach illness. He played 47% of the defensive snaps against the Patriots and had a sack and another tackle for negative yardage.

That he was still productive while ill and with little practice time speaks well for Clark's chances of helping the Chiefs moving forward into the playoffs. Clark said he believes the worst is over for him with regard to the ailment.

"I feel like it is," Clark said. "I had a lot of scans on my stomach, but everything came back negative. I want to play more, of course, but that will come next week or a few weeks after."

That Clark played in the two games at all surprised some of his teammates.

"I didn't think we'd see him out there," cornerback Bashaud Breeland said. "Last week he was throwing up sick and he still goes out there to play the way he did to help us win. He pushed himself [Sunday] the same way. You don't see that a lot and he did it two weeks in a row."

Quarterback Patrick Mahomes said, "It just shows the competitor that he is."

Clark was one of the Chiefs' big offseason acquisitions. They sent their first-round draft pick to the Seattle Seahawks as part of the trade to get Clark, then they gave him a five-year contract worth $104 million.

He didn't live up to expectations early in the season, though, with one sack and little else in the first six games. But Clark said he was playing with a pinched nerve in his neck.

"When I started the season off, I was probably at 20% [effectiveness]," he said. "I had a lot of doctors tell me I shouldn't even start the season, I shouldn't even have been playing.

"I just wanted to go out there ... from the start of the season and just show my teammates and prove to Chiefs [fans] that I'm here to stay and that they know what type of player they're getting in me."

Clark has five sacks in six games since, though he did miss Weeks 8 and 9 because of the pinched nerve.

"There was a lot going on that was slowing me down that wasn't allowing me to be myself," he said. "The type of player I am, I like to play wild. I like to play with a lot of aggression. I play with a lot of flash. Everything comes with confidence with me. That's how it starts. I feel like I'm the best player on the field when I'm on the field. I've got a lot of things to prove. I feel I'm one of the best defensive ends in the league, and I feel I want to be the best when it's all said and done.

"When you eliminate [injuries], then it just comes down to ability. When you put my ability against any offensive tackle in the league, I choose myself over every offensive tackle."

Clark is also helping against the run. He had the biggest play on one of the Chiefs' four fourth-quarter stops in a Week 11 game against the Los Angeles Chargers when he tackled running back Austin Ekeler for a 1-yard loss on a third down. The Chiefs would go on to win by a touchdown.

"That was as important a play as any," defensive coordinator Steve Spagnuolo said. "That's basically what we've been preaching here, and we always do: situational awareness and disciplined play as you venture into November and December. It's very important."

The Chiefs' improved defensive play in the past four games has mostly coincided with Clark's improved play. After starting the season 6-4 and allowing 23.9 points per game, the Chiefs' defense has allowed an NFL-low 11.3 points per game over the past four games. They've also allowed 50 fewer rush yards per game. If the Chiefs can get full games from Clark, they might be capable of more.

"I'm just happy that's all out of the way now and I get to actually go back to playing football," Clark said. "Just being in the hospital and having to get all of these tests done, that's taken a toll on my energy. It feels good to get back to [normal] this week with my teammates.

"[Opponents have] got to keep it coming because I'm going to keep it coming. My neck and a lot of that other stuff is in the past now. So they're getting some football from Frank Clark."