Kansas City, Mo. ? Filling in for a Pro Bowler is a challenge for anyone. Doing it this weekend against the NFL’s fiercest pass rush is Damon Huard’s particular challenge.

The San Diego Chargers, who will visit Arrowhead Stadium on Sunday, lead the league with 21 sacks through five games. Their next target: Huard, who has been the Kansas City Chiefs’ starting quarterback since Trent Green suffered a concussion in the season opener.

“Their front seven is maybe the best in football,” Huard said Thursday. “Their secondary does a good job of not giving up any big plays, so it’s going to be a real challenge for us.”

Huard, who has thrown for 931 yards and five touchdowns since taking over for Green, said the Chiefs’ practice squad defense had done all it could to get the offense ready.

“We’ve got a pretty good scout group,” he said. “They’ve done a good job all week trying to get off the ball, get in my face and harass me.”

But while scout-teamers can simulate the Chargers’ sets and stunts, matching their speed and skills is another matter.

“Practice is practice. You simulate the best you can every time you prepare for an opponent,” coach Herm Edwards said. “What you can’t simulate is the players they have. You can simulate how they blitz, how they bring pressure, but you can’t simulate the three or four Pro Bowl players they have.

Kansas City quarterback Damon Huard (11) throws during the Chiefs' 45-7 loss Sunday in Pittsburgh.

“But the good part about it is, we’ve got some Pro Bowl players too,” he said, “especially on offense, in the line.”

But while guards Brian Waters and Will Shields both went to the Pro Bowl last year, much of the Chargers’ pressure comes from the outside linebacking corps of Shaun Phillips, who has six sacks, and Shawne Merriman, who has 51â2.

And with four sacks, defensive end Luis Castillo is also a threat.

The Chargers won’t focus entirely on stopping the pass, though – not with running back Larry Johnson still a breakout threat despite rushing for only 62 yards over the last two games.

“Teams have been doing a lot to stop him. They’ve been committed to stop the running game. We will be, too,” Chargers safety Marlon McCree said. “He’s a great back, and if we don’t contain him, it’ll be a long day for us. We’ve got to just focus on stopping Larry and see what happens.”

San Diego linebacker Shawne Merriman celebrates after sacking 49ers quarterback Alex Smith on Sunday in San Francisco. Merriman is second on the Chargers defense with 51â2 sacks.

Green got a good medical report this week but is not ready to resume practice, Edwards said.

“He’s getting a little better,” Edwards said. “He’s throwing the ball a little bit now, but that’s all it is. He’s getting better. He’s not ready to play.”

So the job remains Huard’s, while Green remains involved in helping his former understudy develop.

“Trent’s been a great team player through this whole thing,” Huard said. “Obviously he’s a great competitor and he wants to get on the football field, and he’s doing everything he can to do that, but at the same time he’s taken on the role of supporting me and this team and the coaching staff.”