"Andy Roddick's thirst for competition was like no other, when he lost he would keep bugging me" - Serena Williams' ex-coach Rick Macci

Serena Williams' former coach Rick Macci recently opened up on Andy Roddick's competitive spirit as an up-and-coming player.

Invited to speak on the ATP Tennis Radio Podcast, the famous tennis coach asserted that while he had worked with many male players during his heyday, none of them compared to his former ward Andy Roddick as far as his mentality was concerned.

He also disclosed that the American hated losing in his early years, and would always take him up on challenges to prove his competitiveness.

"I did work a lot with Christian Ruud, Vincent Spadea, there's been other guys who didn't become top 10 in the world. But Roddick, his thirst for competition was like no other. The guy was so brutally competitive," Macci said.

"First to get the drink, there would be a smack on the table, he would fight you to get it. When he lost, he would keep bugging me... I said, you gotta earn it. He would come back the following day, I would play him... The wiring to compete, which is the wildcard to handling pressure. When you're all about the competition, you don't choke as much, get as nervous," he added.

Macci then showered rich praise on Andy Roddick's forehand when he was coming up, even going as far as to claim that it was the young American who taught him a lot about the biomechanics of a tennis player's strokes.

"His forehand.. he kinda taught me about the racket going on the outside, the elbow elevated, the pull, the flip, it was a little weird when I saw it work. Then he became biomechanically one of the best in tennis history," he said.

"Andy Roddick was about 6'2" or whatever, when I thought he was going to win the US Open at 19 or 20" - Rick Macci

Andy Roddick serves at the 2003 US Open

During the podcast, Rick Macci also claimed that the American's steep upward growth as a youngster surprised him greatly. He contributed these improvements to his mental strength.

"He was about 6'2" or whatever, when I thought he was going to win the US Open, at 19 or 20. When he grew up at 14-15, his serve just went a whole another level. But it was more the internal," he said.

Andy Roddick, for his part, came up just short in terms of fulfilling his former coach Rick Macci's prophecy. The American won the championship match at the 2003 US Open, after having turned 21 in August that year. He also finished as the year-end World No. 1 in 2003, which remains one of the highlights of his career.

The former World No. 1 went on to compete in four more Major finals, losing them all to his arch-rival Roger Federer. He eventually retired from the sport at the 2012 US Open, at the age of 32.