The shocking thing about what Miami quarterback Dan Marino accomplished today is that it really was not shocking at all. It has been this way for Marino all season.

Marino threw for 421 yards and four touchdowns to lead the Dolphins to a 45-28 victory over the Pittsburgh Steelers in the American Football Conference title game before 76,029 at the Orange Bowl. That arranged a Super Bowl XIX that most observers figured was coming several months ago: Miami (16-2) against San Francisco (17-1) on Jan. 20 in Palo Alto, Calif.

There are several ways in which to gauge Marino's 21-for-32 excellence today, a big-play explosion that set AFC title game records for passing yards and touchdown passes and left the Steelers muttering into the offseason.

Steelers safety Donnie Shell said simply, "They have a helluva passing game, well designed. But it's not the design, it's No. 13 (Marino). I'd rather play (Denver's John) Elway."

Oft-beaten cornerback Dwayne Woodruff said, "Every defense we have, we ran. And some we don't have, we ran."

"Marino is the best quarterback we've seen," Pittsburgh Coach Chuck Noll said. "We had nothing to be ashamed of. They were just too good. It was just too tough to overcome Marino and their passing game."

Marino completed nine passes for more than 25 yards today. With 421 yards passing, he finished 12 yards shy of the league's all-time postseason record of 433 yards set by San Diego's Dan Fouts two years ago. And Marino didn't even throw a pass in the game's final 11 minutes. No need with such a big lead.

But here's the best way of all to gauge Marino's magnificence: start with 2:52 left in the first half, when all-pro receiver John Stallworth eluded safety Paul Lankford to catch a 65-yard scoring pass from Mark Malone to give the Steelers their only lead, 14-10.

The Dolphins -- their season, their records, their quarterback -- were challenged. "When Stallworth caught that pass, there was a lot of tension on our sideline," Dolphins receiver Jimmy Cefalo said.

This is when Marino turned the Steelers' defense to rubble. "Steel Melts at 13," said one bed-sheet banner. Just so, Marino led his Dolphins 77 yards in a five-play drive that consumed 1 minute 22 seconds. Marino finished the drive with a 41-yard scoring pass to wide receiver Mark Duper for a 17-14 lead.

Two plays later, Malone looked for Stallworth curling over the middle. But Malone hesitated just a moment, as inexperienced quarterbacks often will do. This allowed time for safety Lyle Blackwood to make an interception, skidding on his side at the Pittsburgh 35-yard line. There was 1:09 left in the half.

Back came Marino. This time, it took Marino 33 seconds to produce a touchdown.

Marino threw a hard pass between two defenders to tight end Joe Rose, for 28 yards to the Pittsburgh one. Running back Tony Nathan rushed for the touchdown and it was Dolphins, 24-14.

There were still 36 seconds left in the half. There seemed little left in the Steelers. They had played precisely as they had planned in the first half -- they even led in time of possession, 17 minutes to 13, running their trap plays so well -- and still they trailed by 10 points. Marino can do that to a team.

Marino led the Dolphins to touchdowns on their first three drives of the second half. Meaning that, following Stallworth's touchdown catch for that 14-10 lead, Marino directed five consecutive touchdown drives. Next challenge.

"I'd say this was sub-par for Danny. He's capable of throwing eight or nine touchdown passes in a game. Do I really believe that? Of course," said wide receiver Mark Clayton, who caught four passes for 95 yards, one for 40 yards and a score.

Clayton didn't even play in the second half, after suffering a "slightly bruised" shoulder that is not expected to keep him from playing in the Super Bowl. Miami defensive tackle Bob Baumhower said of Marino, "The guy is awesome. We keep waiting for him to come down to earth and play like a mortal."

"I guess we're getting used to this and we hope it just keeps going," said Duper (five receptions for 148 yards and two touchdowns). "Let his game speak for itself."

Miami Coach Don Shula, headed for his sixth Super Bowl as head coach (one with Baltimore), said of Marino, "What more can I say about him that I haven't said already? He takes the defense head on, he attacks . . . When they blitz, he sees it and handles it."

And what exactly did Daniel Constantine Marino, age 23, say when asked to talk about each of his scoring passes? He adjusted a Super Bowl XIX baseball cap handed to him by the team equipment manager and said, "I can't even remember. We just kept doing it."

The Steelers had lost, 31-7, to the Dolphins earlier this season. They decided to gamble more on defense today, blitzing often. Tony Dungy, their defensive coordinator, said, "If you had told me before the game that we would get no sacks and just one interception, then I would have said that we will lose."

The Dolphins also made some changes. "We made so many adjustments," said Cefalo, "that it would take a Harvard Law summa cum laude weeks to figure it all out."

The Dolphins often sent four receivers downfield. "We were thinking deep passes," said Rose, the tight end. "Four guys flying down the middle of the field. If there was man-to-man (coverage), throw to the receiver who has the best shot. If it was zone coverage, throw to the open area."

Duper said, "It was just a matter of Marino guessing right, just like he has all year."

The Steelers, outgained 569 yards to 455, had their chances in the first half. Their first drive ended when Malone threw a potential 40-yard scoring pass for Stallworth. But Malone arched the ball a bit too high, allowing cornerback William Judson to intercept in the end zone.

Stallworth caught four passes for 111 yards and two touchdowns today, accounting for a large piece of Malone's 312 yards passing. Stallworth also passed former Oakland Raiders receiver Fred Biletnikoff to claim two NFL postseason records: most touchdown receptions (12, he had been tied at 10 with Biletnikoff) and most postseason games with more than 100 yards in receptions (five).

Another time in the first half, running back Walter Abercrombie raced 23 yards to the Miami nine. But the play was nullifed by a holding penalty. Then Gary Anderson missed a 53-yard field goal attempt.

"We were possessing," veteran Pittsburgh center Mike Webster said of the first half, "but not converting."

In the end, it was all Marino, though. Today, 17 games after he began the season with five touchdown passes in a 35-17 victory over the Washington Redskins, Marino had his fifth game with more than 400 yards passing. Marino has thrown 55 touchdown passes in 18 games.

Today, in breaking AFC title game records set by Oakland's Daryle Lamonica (401 yards passing in 1968) and by Houston's George Blanda (three touchdown passes in 1960) and the New York Jets' Joe Namath (three in 1968), Marino was simply Marino.

"You almost wonder what Dan will be like when he's 27 or 28," said Miami's veteran guard, Ed Newman. "You know, when he gets into his prime."