La Salle University palayed a tough, sagging man-to-man defense and the sparkling shooting of center Donn Wilber to turn back American University, 86-76, in a key East Coast Conference game last night at Ft. Myer.

The Eagles dropped to 2.2 in the ECC and under .500 over all, at 10-11, for the first time this season. The Explorers remained unbeaten in the conference at 3-0, and are 15-5 overall.

"We have to win at Hofstra next week," said American coach Jim Lynam. "La Salle is very sound team. It's hard to cheat on them inside. Their offense is not designed for the guards to shoot but if you sag inside, they'll shoot."

Wilber's 22 points came on 10 of 14 shots, all from close in. He was virtually unstoppable. Each time the Eagles would start to get back into the game, the lithe senior would manuever inside for a follow-up basket or easy layup.

Two quick inside shots by Wilber, two long jumpers by Tony Di Leo and reserve guard Darryl Gladden, and La Salle had its biggest lead of the game, 63-48, with 10:24 to play.

"My job is to in and run the offense," said Gladden, a freshman from Willinboro, N.J. "At least I try."

Gladden hit six of seven shots and four of five free throws for 16 points in 22 minutes.

He and De Leo, who get 11 of his 19 points after intermission, took pressure off Wilber and freshman Mike Brooks, the Explorers' leading scorer.

Brook finished with 12 points and led all rebounders with 11.

After falling behind by 15 points, the Eagles, urged on by a crowd of 1,480 and the tenacious play of Calvin Brown and Carroll Holmes, rallied to nine points three times.

Held in check by La Salle's Jim Woliewicz in the first half, the 6-5 Brown broke loose for 15 points after intermission. The smooth forward accountered for 12 of American's 19 points during one six-minute stretch. His foot jump shot brought the eagles as close as they were going to get for the last time, 78-69, with some four minutes remaining.

American had no choice but to foul and the poised Explorers took advantage scoring 17 of their final 21 points from the foul line.

Brown finished with 21 points.

"We were behind at the half so I tried to use more defensive players," Lynam said. "But we labored a little on offense. We couldn't get inside on them."

While American was preoccupied with shutting off the talented Brooks, who is averaging 21 points and 12 points and 12 rebounds, Wilber and guard Tony Di Leo carried the LaSalle offense.

Wilber made eight of nine shots and two free throws for 18 points in the first 20 minutes. Di Leo made four of six shots from the outside for eight points.

American got good perimeter shooting from Butch Slappy (11 points) and Brown (six points) to stay close in the first half.

After a layup by Lassoff tied the score at 29 with 7:05 remaining, the Explorers scored six straight points and 14 of the game's next 20 to take a 43-35 lead with 10 seconds left in the half.

American made four shots in the final seven minutes of the opening half, two by reserve gurad Brad Greenberg. His 16-footer at the buzzer cut the La Salle lead to 43-37 at intermission.