Kansas City, Mo. ? LT vs. LJ.

Just sounds like a marquee matchup, doesn’t it?

But while San Diego’s LaDainian Tomlinson is on pace for a 1,300-yard rushing season, with 407 yards through five games, Kansas City’s Larry Johnson has fallen off the form that saw him rush for 1,750 yards – with only nine starts – last season and sparked talk of his going for 2,000 yards this year.

After running for 295 yards in the Chiefs’ first three games, LJ has been all but MIA in the last two. He ran for 36 yards in a 23-20 victory at Arizona two weeks ago and had just 26 yards on 15 carries in last week’s 45-7 loss at Pittsburgh.

And today, when the Chargers (4-1) visit the Chiefs (2-3), Johnson will be facing the NFL’s top defense – San Diego is giving up just 218.4 yards per game – and one of its hardest hitters in linebacker Shawne Merriman. The Chargers are also ranked second in pass defense at 146.8 yards per game and lead the NFL with 21 sacks, meaning Kansas City must establish a running game to keep the Chargers honest on defense.

But then again, San Diego brought the league’s No. 1 run defense to Arrowhead last Christmas eve, and Johnson shredded it for 131 yards and two touchdowns to help the Chiefs win, 20-7, and knock the Chargers out of playoff contention.

“What we did last season on them, it does give us confidence,” Johnson said. “It’s the same guys from last year, so we know we can reproduce the same result.”

This time, Johnson won’t have tackles John Welbourn and Willie Roaf – both retired – to run between. Former Pro Bowl fullback Tony Richardson is also gone, lost to free agency, and quarterback Trent Green hasn’t played since sustaining a concussion in the opener.

The Chiefs have made some stopgap measures at fullback, shifting reserve tight end Kris Wilson to the position and signing free-agent fullback Greg Hanoian to a two-year deal.

No offense to them, but Johnson is preparing to carry the load himself.

“The guys we’ve got right now, they’re brand new,” Johnson said. “One of them is still learning the system and what to do. So as of right now, the way my thinking is, we don’t need one. Even when Tony Richardson was here, we didn’t use him as much as we could have, but the offense still worked.”

Right now, though, the Chargers’ offense is working better. Philip Rivers, the third-year pro in his first year as a starter, has thrown for 1,064 yards and seven touchdowns, with only two interceptions. His 100.6 passer rating leads the AFC and is second in the NFL to the 104.8 rating for Philadelphia’s Donovan McNabb.

“Philip has done a remarkable job,” San Diego coach Marty Schottenheimer said. “He has been throughout. He’s extremely bright, got good leadership skills and plays with a lot of emotion.”

Much as Johnson spent his first two seasons in the shadow of Priest Holmes, Rivers was Drew Brees’ understudy for his first two years in San Diego.

“It was tough at times,” Rivers said. “Not so much because other young players were playing, but because that was all I’d ever done was play the game. Driving to the stadium every Sunday, without a good chance of playing, was not a very good deal.”

Kansas City has improved its defense under Edwards, though, and now ranks fourth in passing defense at 165.8 yards per game.

“It’s a solid group,” Rivers said. “Obviously, it was a disappointing loss for them last week, but we still have our work cut out for us.”