Nick Bollettieri Dead: Famed Tennis Coach of the Williams Sisters and Andre Agassi Was 91

Nick Bollettieri, the famed tennis coach who helped guide Venus and Serena Williams to the top has died. He was 91.

Bollettieri — who also coached household names including Andre Agassi, Maria Sharapova, Boris Becker, Monica Seles and Anna Kournikova — died Sunday at his home after a series of health issues, his manager, Steve Shulla, said in an interview with Associated Press on Monday.

"When he became sick, he got so many wonderful messages from former students and players and coaches," Shulla added. "Many came to visit him. He got videos from others. It was wonderful. He touched so many lives and he had a great send-off."

"Anyone who knew Nick knows how much he loved developing the potential in young people," said Tim Pernetti, president of IMG Academy, which grew out of the Nick Bollettieri Tennis Academy.

"Even in his last days, you could often find him on campus, coaching and mentoring young student-athletes and staff with the same passion and enthusiasm as he did in his 20s," added Pernetti. "Our heart goes out to his wife, Cindi, and his children. He has made a permanent and lasting impact on all of us."

Andre Agassi remembered him with an Instagram post. "Our dear friend, Nick Bollettieri, graduated from us last night," wrote the 8-time Grand Slam winner, alongside a photo of the pair on the tennis court. "He gave so many a chance to live their dream. He showed us all how life can be lived to the fullest."

Born in Pelham, New York, Bollettieri coached tennis on the side while earning a law degree from the University of Miami.

In 1978, he founded the Nick Bollettieri Tennis Academy after borrowing $1 million from a friend to build a live-in tennis academy for his students.

IMG Academy has expanded beyond tennis to help student-athletes achieve their dreams in sports including baseball, football and soccer.

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In his 30-year career as a coach, his students included multiple grand slam winners and ten world No. 1 players. He was also inducted into the International Tennis Hall of Fame in 2014, becoming one of only four coaches to receive the honor.

"I forged my own path, which others found to be unorthodox and downright crazy," Bollettieri said in his induction speech. "Yes, I am crazy. But it takes crazy people to do things that other people say cannot be done."

"The physical and mental part of the game cannot be secondary to your court time," Bollettieri told CNN about his coaching strategy in 2006. "You must have a passion for the game and compete for every single point."