Brian Sipe of the Cleveland Browns went into today's playoff game as the highest rated passer in the National Football League. He came out of it with his I.Q. ranked with temperature by furious fans in Cleveland Stadium, was sat through 3 hours 13 minutes at one degree above zero only to see the quarterback throw away victory.

"Seventy-two yards and nothing," one spectator yelled as he hustled into the 20-mile-an-hour wind. He was referring to the Browns going from their 15-yard line to the Oakland Raiders' 13, where, with 41 seconds remaining, Sipe threw into double coverage and Oakland's Mike Davis intercepted.

That secured a 14-12 victory for Jim Plunkett and the Raiders, placing them in the American Conference championship game against the Chargers at 5 p.m., EST, Sunday in San Diego.

Plunkett spotted the Browns a touchdown in the second quarter when a cross wind hung up his sideline pass to Bob Chandler and cornerback Ron Bolton intercepted and ran 42 yards for six points.

Sipe didn't manage a scoring throw, completing only 13 of 40 for 183 yards and being intercepted three times. But he might have atoned for all that with patience at the finish. He would have had two more shots at a touchdown or a field goal to beat Oakland had he not thrown the ball, on second and nine, almost directly into Davis' hands in the end zone.

Second-guessers also called the Raiders greedy in the fourth quarter. They had reached the Cleveland 15 after Sipe fumbled and Oakland recovered at the 24. On fourth and one, Coach Tom Flores passed up a field goal opportunity that could have increases the Raiders' lead to 17-12.

Fullback Mark van Eeghen was stopped for no gain and the Browns took over with 2:22 to go. But Davis took Flores off the hook with his interception.

Brown defensive end Lyle Alzado, who was knocked out of the game by the flu, said of the ending, "The guys were pretty depressed. Why did he throw such a pass on second down? Don't ask me. Why didn't we kick a field goal, or give the ball to our fullback (Mike Pruitt, who ran for 48 yards on the frozen, slippery field and swept left end for 14 yards to set up the scoring opportunity at the Oakland 14)?"

Al Davis, general managing partner of the Raiders, defended his coach's strategy in passing up the field goal. "If we made a first down there it would have been all over," Davis said. "Neither team had scored going the other way."

Peter Hadhazy, assistant general manager of the Browns, implicitly agreed with Davis in a separate interview. "We were hoping the Raiders would take the field goal then."

As it turned out, the Browns could have beaten the Raiders with three points, but place-kicker Don Cockroft languished on the sideline in frustration.

He had kicked two field goals in four tries, good from 30 and 29 yards, missing from 47 and 30, and had a conversion attempt messed up by a bad snap.

Cockroft had made 16 of 26 tries during the regular season, five of seven between 30 and 39 yards.

Plunkett started out passing tentatively on the frost-bitten field and into the swirling wind, but he completed 14 of 30 for 149 yards and survived two interceptions. He didn't manage a touchdown throw, either, but he set up two one-yard scoring plunges by van Eeghen with big plays to tight end Raymond Chester.

After being intercepted for the touchdown in the second quarter, Plunkett took the Raiders 64 yards to score, starting with a 15-yarder to Chandler and moving the ball to the Cleveland two on a 26-yard pass to Chester. Van Eeghen gave the Raiders a scare by fumbling, but recovered the ball for a one-yard gain, before scoring on the next play. The extra point gave the Raiders a 7-6 lead.

In the fourth quarter, after Cockroft's field goals in the third period put the Browns ahead, 12-7, Plunkett moved the Raiders 80 yards for a touchdown. He passed 18 yards to van Eeghen, 19 to wide receiver Cliff Branch and 27 to Chester, to the Cleveland 15, setting up van Eeghen's second touchdown.

The Browns had three chances to score touchdowns in the third quarter, at the Oakland 12-, 18- and 12-yard lines. Cockroft salvaged three-pointers twice and lost another opportunity when rookie holder Paul McDonald couldn't handle a bad snap from center Gerry Sullivan.

And so the Browns had to settle for the AFC Central Division title, and an 11-6 record, counting today's loss.