Serena Williams' ex-coach, Rennae Stubbs, took a jab at Novak Djokovic for missing out on the hard-court tournaments in America since his appearance at Wimbledon. His absence from these tournaments raised injury concerns and doubts about his chances of winning the 25th Grand Slam title.Stubbs, who had coached Williams in 2022, didn't hesitate to express her concerns about Djokovic's future and underscored how Carlos Alcaraz and Jannik Sinner continue to get the best of him in the final stages of the tournament. His predicted draws for this edition of the tournament also show that he might meet Alcaraz in the semifinal and Sinner in the final.On the Rennae Stubbs Podcast, the Aussie discussed how she doesn't understand why anyone should miss the crucial preparatory tournaments ahead of the US Open. Especially for Djokovic, missing them without citing any clear reason would be costly, considering the challenges that he is going to face at Flushing Meadows. She said:"I mean, we know that he's emphasized the Grand Slams and the major titles and that's all he's really interested in. Butat some point, I don't care who you are, how great you are, you have to play matches, and particularly coming into a best of five...He can't withstand it seems seven matches best of five, because something happens. The Australian Open, he got injured. You know, clearly, Sinner and Alcaraz are getting the best of him in the latter parts of these major tournaments." (12:40 onwards)Novak Djokovic will face Learner Tien in the first round on August 24.Rennae Stubbs predicts Novak Djokovic's last Grand SlamRennae Stubbs predicted that Novak Djokovic's last Grand Slam will be at the Australian Open next year. This verdict came after the Serb failed to make it past Jannik Sinner in his second consecutive Grand Slam semifinals at Wimbledon.In her podcast episode that aired on July 15, Stubbs stated that it would be his best bet, considering he has won the tournament 10 times in his career so far.“I think he [Novak Djokovic] has sort of hinted that the last Grand Slam will be the Australian Open and I think the reason for that is because it has been his most successful, winning it [10] times. I think it’s not a bad way for him to go out if he decides to. It has clearly been the best place for him to win a Grand Slam," she said.However, this prediction might not align with Djokovic's, as he hopes to compete for his country at the 2028 Summer Olympics.