Kansas City, Mo. ? Leonard Pope cradled the touchdown pass from quarterback Matt Cassel with just less than five minutes left in the game, pulling the Kansas City Chiefs within a field goal of the San Diego Chargers in a critical game on the road.

Then he pulled his helmet off, and the penalty flags flew.

Pope was given a 15-yard unsportsmanlike-conduct penalty for taking his helmet off while still on the field. The defense ultimately held, giving Kansas City a chance to win in the closing minutes, but the mental mistake demonstrated a frustrating trend that developed in a 20-17 loss.

For the first time all season, the Chiefs did some things that gave coaches, players and fans reasons to be hopeful. And then they did something moments later to dash that optimism.

“Shooting ourselves in our foot,” fullback Le’Ron McClain said, repeating the old cliché that rings especially true for the defending AFC West champs, who are off to an 0-3 start.

It wasn’t just penalties, though there were certainly plenty of those. But injuries, missed field goals, defensive letdowns and an inability to punch the ball into the end zone after solid, sustained drives all conspired on several occasions to turn positives into negatives.

Kansas City didn’t manage a single first down in the first half against San Diego, gaining all of 34 yards, but came out of the break and held the Chargers to a three-and-out. It gave the Chiefs the ball across midfield and they managed to go the rest of the way for a touchdown.

Rather than make a stand on defense, though, the Chargers marched 80 yards in less than 4 minutes for an answering touchdown, negating any momentum Kansas City built.

On the Chiefs’ ensuing possession, they put together a 21-play drive — if you count penalties — that even impressed coach Todd Haley. But the drive ended when, on third-and-11 from the 18, a run by Thomas Jones up the middle gained just 3 yards and Ryan Succop had to trot onto the field for a field goal. It was a minor letdown after the offense had finally found its rhythm.

“I’ve never been a part of a 21-play drive,” Haley said, “and that was a very positive thing, despite the penalties and only getting three points out of it.”

The Chargers’ defense was worn down and the momentum was swinging back toward the Chiefs, but the defense again couldn’t make a stand. San Diego put together a drive of its own for a matching field goal, giving its own defense a chance to rest while restoring a 10-point lead.

“The defense is very aware after a drive like that, we have a chance to put our offense out against a defense that appeared tired, down on a knee and things like that, and our defense went out and fully intended to get that three-and-out and just pressed a bit,” Haley said.

The list of positives dulled by negatives goes on and on.

Kendrick Lewis picked off Chargers quarterback Philip Rivers in the first quarter to give Kansas City prime field position. Unable to move the ball, the Chiefs settled for a 38-year field goal try that Succop missed wide right.

“Everyone in the locker room is counting on those points,” Succop said.

Later in the half, Brandon Flowers picked off Rivers and returned the ball 43 yards to give Kansas City excellent field position. The young starting cornerback was slow to get up after the play, though, and Flowers didn’t return to the game — even though Haley said he tried.

Flowers said afterward he hurt his ankle on the return and that an injection didn’t do a whole lot to numb the pain. His status for next week’s game against Minnesota is in question.

“He made a big play for us and unfortunately couldn’t continue,” said Haley, who hopes to know whether Flowers will be available for the Vikings later in the week. “I had to drag him off the field once. Our trainers are over helping someone else and I had to drag him off the field.”

The fact Flowers wanted to play through the pain proves how much everyone on the sideline still cares, Haley said. The Chiefs may be winless through three weeks, including a pair of ugly losses to start the season, but there are signs of hope for the first time all year.

Even if most of them have been obscured by misfortune.

“We just need to get over the hump and play Chiefs football,” McClain said. “We’ll be OK.”