On the east side of Mission Bay, the San Diego Chargers are holding the 1980 AFC Western Division title.

On the east side of the San Francisco Bay, the Oakland Raiders are holding the 1980 Super Bowl title.

Running between the two, is the River of Rivalry. This current flows in both directions.

"The rivalry has been here longer than I have," says Don Coryell, the fourth-year San Diego coach whose team tied the Raiders last year at 11-5 but won the division on the basis of net points in division games. "I would say 11-5 will win this division and 10-6 would probably be a tie. You can be sure neither one of us will run away from the other."

Says Tom Flores, the third-year Raider coach, "There has always been something between the two teams. It's just that we're both winning now that people are starting to notice. Last year, San Diego was picked by everyone to win. We were picked last by some people. Maybe our Super Bowl title will get some people to notice us."

A few people noticed the Raiders last year, including the Philadelphia Eagles.

But to understand the race this division promises, you must only look at the Raider-Charger games of 1980. There was as much intrigue as there were points.

The Chargers won the first one in San Diego, 30-24. The Raiders won the second one in Oakland, 38-24. Then the Raiders won the Big One (before the Super Bowl, anyway) in San Diego, 34-27, to eliminate the Chargers in the AFC title game that many said was the real Super Bowl.

San Diego's Dan Fouts threw for an NFL record 4,715 yards. His 30 touchdown passes ranked second best in the league (Steve Bartkowski of Atlanta had 31). Always, there were Jefferson, Joiner and Winslow.

Tight end Kellen Winslow's reception total was as ample as his 6-5, 252-pound physique: an NFL-high 89 catches. John Jefferson's 82 receptions ranked third in the league and Charlie Joiner's 71 ranked sixth. There is fear, however, that Jefferson might not play this year because of a contract dispute. "That worries me," says Coryell.

If Chuck Muncie can stop fumbling his identity and the football, the San Diego offense might be the among the best. James Brooks (Auburn) and a healthy John Cappelletti, in his seventh year, could help Muncie avoid the spotlight and the linebackers' grind.

The San Diego defense give up fewer than last year's 20.5 points per game, which was 10th best in the 14-team AFC. The presence of former Redskin coach Jack Pardeee as defensive coordinator should help.

The Raiders (11-5) don't have such worries. With John Matuszak, Lester Hayes and the rest all returning, why doubt them? Last year, the Raider defense ranked third in the AFC.

The offense is Jim Plunkett's; the questions are Dan Pastorini's, the former starter. Bob Chandler (49 catches), Cliff Branch (44) and Kenny King (761 yards rushing) return also.

It seems more than four calendars ago that Denver (8-8) was in the Super Bowl. Last year, the Broncos were 11th in the AFC in passing and rushing. It is not the sort of consistency of which pride or playoffs are made.

Dan Reeves is the new coach at Denver, replacing Red Miller. Craig Morton will be the quarterback. The Broncos will play Oakland (twice) and San Diego in three of their first five games. For the Reeves staff, it could be a time for an upset on the field or an upset in the stomach.

Kansas City (8-8) rescued last season after an 0-4 start. Quarterback Steve Fuller (2,250 yards, 10 touchdowns, 12 interceptions) and running back Ted McKnight (693 yards) will lead an offense of potential. "I think we will be a much improved offensive team," says Coach Marv Levy with the standard preseason hurrah.

They'd better be. Last year, the Chiefs' defense gave up 336 points, fourth worst in the conference.

Last season, Seattle (4-12) had one of the worst defenses in football, giving up 408 points in 16 games, 13 points worse than the Jets. UCLA saftey Ken Easley, who hits with punishing effectiveness, will help.

Jim Zorn (3,346 yards, 18 touchdowns, 16 interceptions) and Steve Largent (66 receptions) cannot win too many games alone. They didn't last year, anyway; the Seahawks scored 291 points, third lowest in the AFC.