When you coach defense for the Chargers, a sense of humor is useful. Also luck. Tom Bass has both. Having been striken with polio shortly after the Salk vaccine was developed here about a quarter-century ago and seen the offense save San Diego's playoff life today, this jolly published poet shouted to quarterback Dan Fouts:

"I thought you guys scored too soon."

There was a minute left when the gang that first showed us football's future scored its second fourth-quarter touchdown. That proved enough against one of the NFL's proud teams, the Pittsburgh Steelers, and the Chargers won a game of big plays and big blunders, 31-28, to advance to a second-round game against the Dolphins Saturday at 12:30 p.m. in Miami.

Of the 133 plays, 49 fetched at least eight yards. Any little ol' three-yarder off tackle got thrown back. There were 901 yards in all, 55 first downs and five touchdown passes. And the gift James Brooks gave the Steelers on the first play of the game Terry Bradshaw returned early in the fourth quarter.

In between, and later, Chuck Muncie gained 126 yards on a Steelers defense that once rarely surrendered 126 feet on the ground. Still, Bass' defense did contribute.

Sort of.

Bruce Laird intercepted Bradshaw near the goal line to foil an early Steelers drive and Jeff Allen grabbed the pivotal second error that started Fouts flinging for the comeback.

Bradshaw admits the Steelers got too conservative with such a lead so late. Should have kept passing, he said, second-guessing the man who calls every play: himself. But he got on a run fixation, then passed when he should have run on the play that gave the Chargers life.

"A little fuzzy," he said.

Allen's interception and eight-yard return allowed the Chargers to fly 29 yards for the touchdown that put them close with 8:42 left; a 20-yard punt allowed the Chargers to grind 64 yards for the winner. Both touchdowns were to the matchless tight end, Kellen Winslow.

Each was dramatic in its fashion. The first was on fourth and six from the Pittsburgh eight. With Steelers seemingly surrounding Winslow in the middle-front of the end zone, Fouts still got the ball to him.

How big was the target area?

"You want it in yards? Inches?" the quarterback snapped. "Let's say he was open for a split second."

Winslow was more expansive:

"Maybe four yards. You try and find a dead spot in the defense. It's your job to find the dead spot before they find you. Kinda like Pac-man."

The second one, the clincher from 12 yards, was kind of like cheating. A screen, it gave the enormous Winslow the ball with a full head of steam and some escorts. The only Steeler that touched Winslow might still be buried in the end zone turf.

Muncie thought the Chargers' running game has come around just in time, and about time.

"The passing game's been there all along," he said. "During the strike, we practiced only passing. So the running is just coming back." Passing eats up great gobs of yardage; running eats up great gobs of time and keeps the defense where the Chargers prefer it: next to Bass on the sideline.

As Bradshaw emphasized, each offense was "awesome" quite often.

Bradshaw said Laird slickered him on that first interception, which cost the Steelers at least a field goal and very likely a touchdown when they were winning by 14-10 in the second quarter. The quarterback expected the safety to be elsewhere, because he had been a few times earlier on similar formations.

"What one old dog does to another," Laird said.

Philosopher Bass was asked if it would be embarrassing for the Chargers to make the Super Bowl when nearly everybody insists they are defenseless. He laughed, threw back that large, bearded face, grabbed some of a massive belly and said:

"I don't care how we get to the Super Bowl. If we get to the Super Bowl, and we can't play defense, it will be one of the greatest accomplishments in (the history of) football." San Diego 3 14 0 14 31 Pittsburgh 14 0 7 7 28

P--Ruff fumble recovery in end zone (Anderson kick)

SD--FG Benirschke 25

P--Bradshaw 1 run (Anderson kick)

SD--Brooks 18 run (Benirschke kick)

SD--Sievers 10 pass from Fouts (Benirschke kick)

P--Cunningham 2 pass from Bradshaw (Anderson kick)

P--Stallworth 14 pass from Bradshaw (Anderson kick)

SD--Winslow 8 pass from Fouts (Benirschke kick)

SD--Winslow 12 pass from Fouts (Benirschke kick)

A--53,546 Chargers Steelers First downs 29 26 Rushes-yards 29-146 23-97 Passing yards 333 325 Sacks by-yards 0-0 0-0 Return yards 79 102 Passes 27-42-0 28-39-2 Punts-average 1-48 2-33 Fumbles-lost 3-2 1-0 Penalties-yards 6-51 6-54 Time of possession 30:23 29:37 INDIVIDUAL STATISTICS

RUSHING--San Diego: Muncie 25-126, Brooks 3-20, Cappelletti 1-0. Pittsburgh: Harris 10-35, Pollard 9-47, Hawthorne 2-3, Bradshaw 2-12.

PASSING--San Diego: Fouts 27-42-0, 333 yards. Pittsburgh: Bradshaw 28-39-2, 325.

RECEIVING--San Diego: Joiner 5-68, Chandler 9-124, Sievers 2-17, Brooks 1-4, Winslow 7-102, Fitzkee 1-8, Cappelletti 1-minus 2, Muncie 1-12. Pittsburgh: Smith 1-40, Cunningham 5-55, Harris 11-71, Stallworth 8-116, Pollard 2-29, Swann 1-14. Picture 1, Chargers tight end Kellen Winslow runs over Steelers' Mel Blount for winning touchdown. AP; Pictures 2 and 3, Quarterbacks Dan Fouts, of the Chargers and Terry Bradshaw of the Steelers are grimacing on sidelines. Fouts later had reason to smile. AP