Dennis Johnson, a brilliant defensive player who helped propel theSeattle SuperSonics and the Boston Celtics to N.B.A. championships, died yesterday in Austin, Tex. He was 52.

Fred Jewell/Associated Press

Dennis Johnson, against the Chicago Bulls on March 17, 1979, was called “the best backcourt defender of all time” by Magic Johnson

The cause was a heart attack, the National Basketball Association said.

Johnson, a five-time All-Star guard, was in his second season as coach of the Austin Toros of the N.B.A. Development League. He collapsed outside the Austin Convention Center after a team practice and never regained consciousness, Perri Travillion, a spokeswoman for the Toros, a Celtic affiliate, told The Associated Press.

Playing 14 seasons in the N.B.A. with the Sonics, thePhoenix Suns and the Celtics, Johnson, known as D. J., was quick with his hands. He was named to nine consecutive N.B.A. All-Defensive teams.

He was the most valuable player of the 1979 N.B.A. finals, against Washington, when he helped take the Sonics to their only league championship. He played on Celtics teams that won titles in 1984 and 1986.

“Dennis was a great player, one of the best teammates I ever had,” the Celtics’ Hall of Famer Larry Bird, now president of the Indiana Pacers, told The A.P. yesterday.

When the Celtics retired Johnson’s No. 3 in a Boston Garden ceremony in December 1991, Magic Johnson, the retired Los Angeles Lakers star, sent a telegram calling him “the best backcourt defender of all time.”

In the 1984 N.B.A. finals, Dennis Johnson played terrific defense against Magic Johnson. He made a jumper just before the final buzzer to win Game 4 of the 1985 finals against the Lakers.

Bird and Dennis Johnson teamed up on a memorable play in Game 5 of the 1987 Eastern Conference finals against the Detroit Pistons. Bird stole an inbounds pass from Isiah Thomas under the Celtics’ basket and passed to Johnson, who made a driving layup for the victory. The Celtics captured the series in seven games but were beaten by the Lakers in the finals.

Bill Laimbeer, the center on that Pistons team, told The A.P. how Johnson “played with passion and grit” and called him “a great player on a great ballclub.”

Johnson had 15,535 career points (averaging 14.1 points a game) and 5,499 assists (5.0 a game). When he retired after the 1989-90 season, he was the 11th player in N.B.A. history with more than 15,000 points and 5,000 assists. He was named to the All-N.B.A. first team in 1981.

That Johnson would even play in the N.B.A., let alone become a star, was hardly evident when his college days ended. A native of Compton, Calif., and one of 16 children, he saw little action playing at Dominguez High School in Compton. He was a 5-foot-9 guard then — 7 inches of growth still ahead. He played two seasons at Los Angeles Harbor Junior College before moving on to Pepperdine. He finally gained attention when he averaged 15.7 points a game in leading Pepperdine to a top 20 ranking and a spot in the 1976N.C.A.A. tournament.

The Sonics were impressed by Johnson’s strong defense in the tournament and made him a second-round draft pick.

Having left college after his junior year, Johnson had an unspectacular rookie season. But he developed into an outstanding defensive guard when Lenny Wilkens, the former N.B.A. star guard, became the Sonics’ coach.

Johnson played four seasons for the Sonics and three with the Suns, then joined the Celtics in the 1983-84 season.

He became a fixture on the Celtics teams of the 1980s, teaming with Bird, Kevin McHale, Robert Parish, Danny Ainge and Bill Walton.

“He was one of the most underrated players in the history of the game and, in my opinion, one of the greatest Celtic acquisitions of all time,” Ainge, now the Celtics’ executive director of basketball operations, said in a statement yesterday.

When the 1989-90 season got under way, the Celtics named John Bagley their starting point guard. Johnson was 35, and it seemed he was near the end. But when Bagley dislocated a shoulder, Johnson stepped in and he seemed rejuvenated.

“He’s been our glue man,” Coach Jimmy Rodgers told The Worcester Telegram and Gazette.

“If you want to say I’m old, I’m old,” Johnson told the paper. “But you don’t have to say that I’m decrepit.

“My game revolves around the other four guys out there,” he said. “I’m not a great shooter, I don’t think of myself as a great passer or a great ball-handler, but I think of myself as average in every category. I think that’s what enabled me to last this number of years.”

Johnson was an assistant coach with the Celtics from 1993 to 1997. He spent four-plus seasons as an assistant with the Los Angeles Clippers and was their interim head coach for the final 24 games of the 2003 season, taking over for Alvin Gentry.

After working as an advance scout for the Portland Trail Blazers, Johnson was named head coach of the N.B.A. Development League’s Florida Flame in 2004-5. After one season with Florida, he became the Toros’ coach.

Johnson is survived by his wife, Donna; his sons Dwayne and Daniel; and a daughter, Denise.

Johnson reveled in the opportunity to star in the playoffs.

“There’s nothing better than being the last two teams on the court in the whole N.B.A. and having everyone else watching you,” he told The Atlanta Journal-Constitution in 1988. “After you win those games, walking off the court, you’ve got the best smile on your face you’ll ever have, the most excitement you’ll ever feel.”