The Celtics learned to play without David Cowens through the first two months of the season and they learned to play without him again last night.

Cowens retired midway through the second quarter last night with a back injury, but the Celtics nevertheless managed to lead, 63-53, at the half.

The Knicks rallied behind the shooting of Walt Frazier and Mo Layton to take an 88-86 lead with a mere period left to play.

Veteran John Havlicek, who had been playing in the backcourt in the first three periods, moved to the front line for the decisive fourth quarter.

The visiting Knicks ignored the switch at first, padding their lead to 96-90 before the Celtics' playoff desire took hold. Providence grad Kevin Stacom moved into the backcourt with Olympic-champion Jo Jo White to spark the Celtics in their late drive.

But with Stacom scoring eight points in the decisive fourth period and Havlicek and sudden super-sub Sidney Wicks adding five points each, the Celtics overhauled the Knicks for a 119-111 final.

Havlicek finished with 25 points for the defending NBA title-holders while ex-Trailblazer Wicks added 21, White chipped in with 20, and Curtis Rowe and Stacom each notched 12 points each for the victors.