In a way, it's the oldest rivalry in the nation.

When Harvard plays William & Mary today in the Stadium, America's two oldest colleges will see which team has gotten better with age.

And both teams have aged awfully well. William & Mary is the fifth-ranked Division 1-AA squad in the nation, and the Crimson snuck into the top-20 this week after its big win over UMass.

Although this is a non-Ivy contest for Harvard, today's game could be, in many ways, the most important test of the year.

"William & Mary is the toughest team we'll play all year," Crimson Coach Joe Restic said yesterday. "This win could do a lot for us. We're going after it."

If Harvard wins, its national ranking and confidence for the Ivy schedule will rise tremendously. But beating the Tribe will be a tough accomplishment for the Crimson, which hasn't faced a team as talented as William & Mary for some years.

And Harvard, depite its number 16 ranking--the highest since 1982--has some real question marks.

The offensive line, which has played well in spurts, will consistently have to open holes for the backs, and protect quarterback Brian White in order for the offense to click. Restic's Multiflex has yet to kick into gear this year, and for Harvard to stay close today, the offense must control the ball.

Another key will be the play of senior fullback Robert Santiago, who is having a sub-par year thus far. Santiago, an unstoppable runner when he gets some room, hasn't gotten much this year, and last year's Ivy rushing leader has compiled only 82 yards in 1985.

White, too, has had a disappointing first two games, with only a .360 completion rate and 18 yards on the ground.

"We have to be able to balance our attack," Restic said of his offensive strategy. He predicted that Air Crimson will finally take off today, taking some pressure off Santiago, speedster Rufus Jones, and the rest of the talented Harvard backfield.

William & Mary is a little weak on defense, but the offense boasts very dangerous, very wide-open attack.

Quarterback extraordinaire Stan Yagiello is the best signal-caller the Crimson will face all year. Yagiello threw for over 400 yards last week, and unless the strong Harvard secondary plays to its full potential, he'll pick it apart.

The Tribe's other big performer is tailback Michael Clemon, a 5-ft., 5-in., 165-lb. waterbug whom Restic said the Crimson "must take away."

Coach Jimmye Laycock has turned W & M into a legitimate 1-AA power this season. The Tribe sports a 3-1 record, including a victory over Delaware--which was the top-ranked preseason 1-AA team--and a loss to Division 1-A Wake Forest by only a touchdown.

Harvard has two impressive wins this year; a 49-17 drubbing of Columbia, and a 10-3 upset of UMass in which the defense turned in a virtuoso performance.

Captain Brent Wilkinson is a gutsy, inspirationial leader at linebacker, and a corps of hard-nosed defenders--including backer Scott Collins, safety Cecil Cox, and cornerbacks Ken Tarczy and Lee Oldenburg--lead one of the hardest-hitting units around.

The Crimson defensive line, however, is inexperienced. Nonetheless, since the first half of the Columbia game--when Lion quarterback Henry Santos sat in the pocket and tore the secondary to shreds--the pass rush has looked adequate.

Pressure from the front five will be crucial in stopping Yagiello from his aerial antics, but if the defensive line doesn't come through, Restic has another plan.

"If we don't get the pressure, we'll have to blitz and play man-to-man," he said. "That's our strength."

Restic, who last week became the winningest coach in Harvard history, is 2-0 lifetime against William and Mary, with his last victory coming in 1981. Before 1980, the teams hadn't met in almost 40 years.