Rick Pitino left one of college basketball's most storied teams to join professional basketball's most fabled franchise yesterday when he resigned after eight seasons at Kentucky to become the coach of the Boston Celtics.

Pitino, 44, agreed to a reported 10-year, $70 million contract that would make him the highest-paid coach in any sport. Pitino said he is not a part owner of the team, but various reports have indicated that he will have control of basketball operations. His jump comes a day after Larry Brown left the Indiana Pacers and signed a five-year, $25 million contract to take over the Philadelphia 76ers.

Pitino replaced M. L. Carr, who quit last week after the Celtics finished with a franchise-worst 15-67 record. Carr remains as director of basketball operations.

"I don't have an easy path. I have a very difficult one," Pitino said at a news conference yesterday afternoon in Lexington, Ky. "I could stay and coach at Kentucky and be very happy, but there's a challenge out there that I want to take. It's a monster challenge."

Two of Pitino's assistant coaches at Kentucky, Jim O'Brien and Winston Bennett, will join him in Boston, Pitino said. But the future of Boston legend Larry Bird remains unclear. Bird, who is a special assistant to the Celtics, has a four-year offer to coach the Pacers worth $4.5 million per year.

When asked if he wants Bird to remain with the Celtics, Pitino said: "Very much so, but Larry's got to want to be part of it. He's got to find out whether he wants to coach or be in management. We need to talk and I certainly will have discussions with him in the hours to come."

Pitino rejected an offer from the New Jersey Nets a year ago that reportedly would have paid him $28 million over five years and made him a part-owner of the team.

He leaves Kentucky after compiling a record of 219-50, including a national championship in 1996. The Wildcats lost to Arizona in the NCAA tournament final in Indianapolis in March.

Kentucky forward Scott Padgett said that while the players hate to see him go, they understand his reasons for leaving Kentucky.

"Everybody knows he had to leave because he likes to take on challenges," said Padgett, according to the Associated Press, adding that several players cried when Pitino broke the news to them. "We felt we couldn't take that away from him because he's given us so much."

Pitino, whose overall record is 442-198, took over at Kentucky after two seasons with the New York Knicks in which the Knicks went 90-74 and won the Atlantic Division title in 1989. He was a Knicks assistant in 1983-84 before moving to Providence.

"I came to Kentucky for a specific reason -- to try to build a program in shambles to the championship level -- and we've accomplished that," said Pitino, who took over at Kentucky shortly after the team was placed on NCAA probation for recruiting violations. The Wildcats were banned from television his first season and from competing in the NCAA tournament for two seasons.

"Now," Pitino said, "I have a similar situation at the professional level that I had eight years ago at this level: something full of glory, full of tradition, full of wonderful pride that I'd like to see get back to the championship level."

In the Celtics, Pitino inherits a team whose leading scorer last season was rookie Antoine Walker, who played for Pitino at Kentucky. Winners of an NBA-record 16 championships, the Celtics will have two picks in the first round of the NBA draft: their own -- a lottery pick -- and one from the Dallas Mavericks, who got the pick from the Minnesota Timberwolves.

Pitino will return to the Northeast, where he spent four years as an athlete at Massachusetts, five years as coach of Boston University and two years as coach at Providence.

"You have to change your coaching style," he said of the move to the professional ranks. "I did that when I went from Providence to the Knicks. But you have to understand I'm not a big believer that players are different. . . . Young kids always change, but you have to change with them as a basketball coach. You have to motivate accordingly, and I look forward to the challenge."

Pitino's contract at Kentucky ran through the 1999-2000 season. While his base salary was $150,000, the total annual package was valued at more than $2 million a year and included a $1 million bonus for staying until it expired.

His new contract stipulates that he will remain with the Celtics after his coaching days are through. Pitino said Boston will be the final stop on his coaching journey, assuming he is successful.

"If we win," he said, "I'll grow old here." CAPTION: The Pitino File RICK PITINO'S COLLEGE AND PRO COACHING RECORD Boston University (1978-83) 91-51 Providence College (1985-87) 42-23 New York Knicks (1987-89) 90-74 Univ. of Kentucky (1990-97) 219-50 Total College 352-124 (.739) CAPTION: MONEY, MONEY, MONEY SALARIES OF THE TOP-PAID PROFESSIONAL COACHES BASKETBALL

Rick Pitino, Boston Celtics, signed a deal yesterday reportedly worth $70 million over 10 years. Larry Brown, Philadelphia 76ers, signed a five-year deal this week reportedly worth $25 million. Pat Riley, Miami Heat, signed a five-year deal in 1995 reportedly worth more than $30 million, including $3 million in annual salary and 10 percent ownership of the team. John Calipari, New Jersey Nets, signed a five-year deal in 1996 reportedly worth $15 million. FOOTBALL

Bill Parcells, New York Jets, signed a six-year deal in February. He originally sought a $10 million, three-year deal. So doubling the length to six years could earn him $20 million, more than any other NFL coach. Jimmy Johnson, Miami Dolphins, signed a four-year, $8 million contract in 1996. BASEBALL

Jim Leyland, Florida Marlins, highest-paid manager, signed a $7.5 million, five-year contract in 1996. HOCKEY

Jacques Lemaire, New Jersey Devils, highest-paid NHL coach at $750,000 a year. CAPTION: "I could stay and coach at Kentucky . . . but there's a challenge out there that I want to take," says Rick Pitino. "It's a monster challenge." CAPTION: Rick Pitino, who celebrated a national championship with Kentucky in 1996, says the same challenges await in Boston and, he hopes, the same result in his second pro stint -- an NBA title.