Former coach Rick Macci has revealed he was not surprised by Serena Williams' decision to retire as he insisted the star is 'going to go out with a bang' at the US Open
The 23-time Grand Slam singles champion has called time on her career, announcing her decision in next month's Vogue.
Adoring tennis fans took to social media to claim they were emotional after the announcement Tuesday and honored the 40-year-old, describing her as the 'Greatest Of All Time'.
But Macci, who coached Williams and her sister Venus at the beginning of their careers, claimed he was not shocked by the news.
'It doesn't surprise me,' Macci told TMZ. 'Listen, she's doing this on her terms. She has a lot of things going on.
'I'm just happy for her because she's making the decision and she's doing it on her terms.
'It's not an injury, she's not hanging on too long or anything like that, but what I really like it's gonna end at the US Open. That's where she won her first Grand Slam and people in New York love it.
I think it's gonna be a must-see TV and knowing Serena, she's gonna go out with a bang.'
Macci sent a special message to Williams as he said: 'You're doing it on your terms. Most of all, you're happy and that's the most important thing.'
'You've influenced so many people's lives, you have no idea. Not just people playing tennis and to me, I think your greatest act is yet to come.'
The US Open is expected to be Williams' final tournament before she steps away from tennis and her shock announcement sparked an unprecedented demand for tickets earlier this week.
However the reality of her retirement appears to already be hitting her as she struggled to contain her emotions in Toronto following her Canadian Open defeat by Belinda Bencic.
A day after announcing her plan to retire, Serena Williams was beaten in straight sets by her Swiss opponent in the second round as one of the final pages in her remarkable career drew to a close.
Related video: Can Serena Williams Win the US Open? (Stadium)
Bencic dropped just six games in a 6-2 6-4 victory where Williams showed flashes of her best, but no more. Her opponent stayed composed, refused to let the gravity of the match unsettle her and advances into round three.
Speaking on court afterwards, Williams thanked her fans in Canada for their support across the course of her playing tenure but found it difficult to hold back the tears.
'Thank you,' she said, her voice crackling. 'It was a lot of emotion, I love playing here and always love paying here.
'I wish I could have played better but Belinda played so well today. It has been an interesting 24 hours.'
Williams told Vogue she did not like the word 'retirement' and instead said she was 'evolving away from tennis, toward other things that are important to me' such as family and business.