Captain John Havlicek, playing in the National Basketball Association playoffs for the 11th time of his career, scored 30 points as the Boston Celtics began defending their NBA championship last night with a decisive 123-106 victory over the Houston Rockets.

The Celtics, idle for eight days since the end of the regular season, came alive after a sluggish start and went in front to stay on three consecutive baskets by Havlicek midway through the opening period.

Boston, playing on their home-court and heavily favored over the Rockets in the best-of-seven Eastern Division semi-final series, led 63-52 at the half and then swept Houston off the court in the final two periods.

Havlicek, who has played on eight NBA championship teams since joining Boston in 1961, scored 10 points in the first period and eight in the second. He consistently set up plays off Boston's fast break. He went scoreless in the third period before finishing with 12 points in the fourth. He also had nine assists and five rebounds in one of his finest performances.

Jo Jo White had 24 points for the Celtics, who will try to make it two in a row over Houston Wednesday night.

Cowens Scored 17

Dave Cowens scored 17 points and dominated the boards for Boston while Don Nelson and Paul Westphal contributed an additional 14 points apiece. Don Chaney followed close behind with 12.

The Rockets, who surprisingly eliminated the New York Knicks in the opening round of the playoffs to earn a shot at Boston last night, were led by Rudy Tomjanovich with an impressive 30 points.

Calvin Murphy, who found himself outside most of the game, scored 19 points.