PITTSBURGH (AP) _ They weren't supposed to start the season 6-0, they weren't expected to make the playoffs, and the San Diego Chargers certainly weren't considered to be a Super Bowl team.

But the Chargers found a way past Pittsburgh's new Steel Curtain. They couldn't go through it or around it, so they went over it, and charged into their first NFL championship game.

Dominated nearly the entire game by the Steelers' blitz and unable to convert on third downs, the Chargers won by beating the blitz on a third-down, 43-yard touchdown pass from Stan Humphries to Tony Martin with 5:13 remaining. That sensational play gave San Diego a 17-13 victory for the AFC championship, denying Pittsburgh a fifth trip to the Super Bowl.

``It says a lot about this team that we stuck together through thick and thin, with thousands of people against us,'' Martin said. ``Nobody ever gave us a shot. We can put that behind us and go to the Super Bowl now.''

They go to the big game burdened by the AFC's 10-year losing streak, and go as 17 1/2-point underdogs to San Francisco, which defeated Dallas 38-28 in the NFC championship game later Sunday. The 49ers routed the Chargers 38-15 in San Diego on Dec. 11.

But the Chargers insist they are not the Buffalo Bills, losers of the last four Super Bowls, or the Denver Broncos, who contributed three dreadful performances to that string of futility.

``I think these two teams have the right kind of style to go against the NFC in the Super Bowl,'' Humphries said.

Both had the style, only San Diego _ a 30-1 shot to win the Super Bowl at the start season _ had the fortitude on Sunday.

``We've been underdogs all the way through the season,'' All-Pro linebacker Junior Seau said. ``The character on this squad is enormous. You just can't measure it.

``You have to do something rare to get respect in this league.''

How rare it was on this warm, wet day, that the Chargers would overcome a record crowd, a superb defense that had shut them down most of the way, and their history of postseason flops.

``Well, we've talked all year long about the playing,'' said coach Bobby Ross, who has turned around a franchise that won the AFL title in 1963, then made only two losing trips to the conference championship in the next two decades. ``The talking doesn't do it. Our guys never stopped believing.''

Right down to the final minute. The Chargers withstood a last-gasp Steelers' drive that carried to San Diego's 3-yard-line. Linebacker Dennis Gibson twice knocked down passes in the end zone _ the last on fourth down _ preserving the Chargers' biggest NFL victory.

``It was like they already had plans for the Super Bowl,'' cornerback Darrien Gordon said. ``The one thing you don't want to feel is not respected.

``They had no respect, they had their Super Bowl rap and their towels and they made excuses for the loss at San Diego.

``But we're the ones going to Miami.''

The Chargers, who were the league's last unbeaten team, will face the four-time Super Bowl champion 49ers on Jan. 29 at Joe Robbie Stadium.

``We don't know how good we are,'' defensive tackle Reuben Davis said. ``We've been up and down all year.''

After Gibson's gems, several Chargers whipped out Terrible Towels to begin their celebrations. Meanwhile, the Three Rivers Stadium record crowd of 61,545 that came expecting to relive the 1970s, fell silent and began filing out.

``This is like a dream or something,'' Davis said. ``We got a couple of those Terrible Towels in our bag. We are going to take them and burn them. We are going to burn them at the Murph. Burning down the house with the Terrible Towel.''

It was the second exceptional comeback for the Chargers. Last week, at San Diego Jack Murphy Stadium, they trailed Miami 21-6 and rallied to win 22-21. This time, despite going 1-for-8 at one point on third downs and rarely giving Humphries enough protection, they struck for two big plays to turn it around.

The first came on a blown coverage during a blitz by Pittsburgh, leaving Alfred Pupunu wide open down the right sideline for a 43-yard TD.

``We went for the run,'' safety Carnell Lake said. ``I have to think run in that situation, because if you don't there is nobody there to stop the run.''

There was nobody there to stop the pass, either.

The only one who could have stopped the game-winning pass was cornerback Tim McKyer. A winner of two Super Bowls with the 49ers, he had single coverage on Martin. Humphries threw the ball high and deep and Martin grabbed it beyond the desperate reach of McKyer.

After the game, McKyer, bent over and wobbly, needed help to walk off the field. At the same time, the sensational Seau embraced Steelers quarterback Neil O'Donnell.

``He just wished us the best in the Super Bowl,'' Seau said.

After the Steelers took a 13-3 lead on Gary Anderson's second field goal, a 23-yarder early in the third quarter, San Diego finally broke through on Pupunu's score.

Amazingly, despite being thoroughly outplayed, San Diego still was in the game. The Chargers had completed one pass to a wide receiver, yet were in striking distance because of Steelers mistakes, particularly holding penalties deep in San Diego territory.

Then Humphries, who was severely outplayed by O'Donnell, took them 80 yards to victory _ and the Super Bowl.

``Everybody said that we couldn't beat these guys,'' Gibson said. ``If we all stick together and play the best we can, we'll have a good chance to win it all.''

The Steelers certainly didn't expect such a swift ending to their superb season. Not with a 415-226 yardage advantage. Or a 22-13 edge on first downs, including 11-for-20 on third down conversions. Not after getting off 80 plays to 47 for San Diego.

``There's a very empty feeling right now,'' said Steelers coach Bill Cowher. ``I guess you can say the further you come, the harder it is to fall.''

Even though the Chargers beat Pittsburgh 37-34 in the season finale, they were 8-point underdogs. The Steelers finished with the No. 1 rushing game in the NFL and the No. 3 pass defense, even though they sat out four key players at San Diego.

But the pass defense fell apart at the worst times and the runners were stymied by Seau and a powerful front line _ Barry Foster gained only 47 yards as Pittsburgh rushed for 66.

It was left to O'Donnell to get them to Joe Robbie Stadium on Jan. 29. O'Donnell set AFC championship game records by going 32-for-54. He threw for 349 yards and a touchdown.

O'Donnell, the man many believed could keep the Steelers out of the Super Bowl, nearly passed them there instead.

``I never was a big stat guy and never will be, so (the records) mean nothing,'' O'Donnell said. ``You could throw for 550 yards and it doesn't matter unless you win.''

Steelers receiver Ernie Mills also had a career day with eight catches for 106 yards. Mills converted five third downs, including two catches of 19 yards and two of 18.

Typically, the Steelers had the ball for 37:13. Untypically, they didn't take full advantage of the possession differential.

``Is it a shock? Yeah it's a shock,'' receiver Andre Hastings said. ``The whole game we believed we won the game. They won the game with big plays.''

Not in the first half, when Pittsburgh made the key plays, including stopping 245-pound running back Natrone Means three times at the Steelers' 2 after a 46-yard pass interference penalty.

Means, the only 1,000-yard rusher in the game, was held to 69 yards on 20 carries. Humphries was 11-for-22 for 165 yards and one interception.