It is said that the mark of a good football team is that it wins on its bad days. If that is true, then undefeated Navy's 9-0 victory over William and Mary yesterday proved the Mids are very, very good because their offense was very, very bad.

Navy's defense, ranked No. 1 nationally in yards and points yielded, seemed to be on the Navy Marine Corps Memorial Stadium field all afternoon. And it repulsed every Inpenalty that nullified a W&M touchdown shortly before halftime.

Navy, 6-0 scored all its points in the second half, on Bob Tutas 27-yard field goal late in the third quarter, following Phil McConkey's 46 yard punt return, and on fullback Larry Klawinski's 33-yard run off right tackle with 4:30 to play.

But, for the first time this season, it was not a day for Navy's offense. Tata missed two of three attempted field goals; quarterback Bob Leszczynski's passes were not accurate and the offensive line failed to block to its usual high standards.

As the game progressed, Navy's offense became more conservative. The Mids face three tough opponents in the next four weeks, starting with Pittsburgh here Saturday, but the idea was not to keep Navy's offense under wraps.

"I felt like I wanted to make some first downs on the ground so we could keep the defense off the field for awhile," said Coach George Welsh.

"When you are from Navy," said Tata, the 5-foot-6 place kicker, "your never hold anything back. Wins aren't that easy to come by. We tried not to look forward to Pittsburgh and most of the guys weren't. Maybe some were. Maybe William and Mary was as good as us. We certainly weren't holding anything back."

Navy did have the ability to come up with the big plays: McConkey's punt return, Klawinski's touchdown run, cornerback Chuck Zingler's three interceptions, Art Ohanian's punting that earned him the game ball.

"If we could come up with a big play. I'd jump for joy," said William and Mary Coach Jim Root.

The Indians moved the ball consistently against Navy, their 210 yards the most against the Mids this season. But they gained more than nine yards on only one play.

In the first half, W&M had the ball in Navy territory for all but 10 of it's 36 plays. But the quickness of Navy's defensive line usually forced quarterback Tom Rozantz to hurry. He underthrew and overthrew his receivers.

One pass he did complete was the play that William and Mary rooters in the crowd of 20.193 will say took away much of the Indians' momentum.

Ohanian's only bad punt of the game, a 15-yarder following a poor snap, had given the Indians possession at their 38 late in the second half. Following steady running by Andy Banks, Alvis Lang and Clarence Gaines, the Indians faced third and eight at the Navy 10.

Wide receiver Ed Schielfelbein took two steps into the Navy end zone, abruptly pivoted with startled Navy defender Zingler behind him and caught Rozantz's perfect pass for what apparently was a touchdown. Rozantz had gone to the sideline before he discovered that a flag had been thrown.

Indian center Pete Pfeffer had strayed more than the allowable two yards beyond the line of scrimmage.

"I wasn't really blocking anybody," Pfeffer said later. "It was a reach block for me. The momentum took me downfield. When I realized it. I dropped to my knees. There was nothing I could do. I was excited. I reached up because their nose guard (Terry Huzel) is pretty quick."

"That took a lot of zing out of us," said Root. "It's touch to score against them anyway, and when you do and they call it back, it's really popping the bubble."

Navy still needed more than 10 minutes of the third quarter to get on the scoreboard. Ironically, on McConkey's punt return. Herb Wilson was yelling for his teammate to make a fair catch.

"One guy was coming down. I could "feel' him, but I couldn't see him," McConkey said. "I felt I could go."

The first Indian to get to McConkey ran right by the Midshipman, at Navy's 40. Then, behind a wall of blockers. McConkey sprinted parallel toward the far sideline, turned left upfield and finally was downed at the W&M 15. Tata then kicked the field goal on fourth down.

William and Mary took the ensuing kick off and, in 11 plays, the Indians were facing second and eight at the Navy 32. Rozantz called a pass to Andy Taffro, who had to wait for the ball so long Zingler stepped in front of him and intercepted it. Zingler returned the ball 54 yards, but Tata ended up missing a 29-yard field goal.

After a W&M punt, Navy's offense finally rolled, driving 71 yards in six plays for the game's only touchdown. Five successive plays involving Steve Callahan set up Klawinski's quick hitter over tackle and he dragged one defender the final few yards with him.