Serena Williams' husband Alexis Ohanian has fired another shot at Madrid Open owner Ion Tiriac after Williams booked yet another Australian Open semi-final appearance.Williams was in imperious form in her quarter-final clash against Simona Halep, thoroughly dismantling the No.2 seed en-route to a 6-3 6-3 win at Rod Laver Arena.Watch the Australian Open with live streams of every court at 9Now. Click here to start watching!The 39-year-old has looked extremely sprightly after being forced to pull out of the French Open early last year through injury, chasing down balls defensively with the same ferocity she did earlier in her career. Williams' vintage showing so far in the Australian Open has silenced many of her critics who believed her chances of winning another Grand Slam title were slim, with Tiriac one of the more vocal critics.Williams was in untouchable form against Simona Halep in her Australian Open quarter-final clash (Getty)Following Williams' dominant display against Halep and advanced to her 40th Grand Slam semi-final, Ohanian made sure to stick the boot into Tiriac on social media."Good thing no one listens to that racist sexist (clown) Tiriac," he tweeted.The tweet wasn't the first time Ohanian had taken aim at Tiriac and called him racist and sexist, after also doing so late last year when Tiriac called out Williams' physique."At this age and the weight she is now, she does not move as easily as she did 15 years ago," Tiriac said on Romanian TV."Serena was a sensational player. If she had a little decency, she would retire." Williams' improved lateral movement has stood out so far in her Australian Open campaign, with her agility a far cry from the version of her fans saw in Melbourne Park last year when she was hampered by ankle and Achilles issues.Williams' coach Patrick Mouratoglou admitted this week that her withdrawal from the French Open last year had allowed the 23-time Grand Slam winner to get out of a "vicious circle".Williams' lateral movement has been noticeably improved after she had been hampered by injuries (Getty)"We've been struggling those last years because she had a lot of injuries, so she was not able to practice the way we wanted," he said."It's a bit of a vicious circle because when you can't practice well, you don't get fit. When you're not fit, you get more injured. We had to get out of this vicious circle."In Roland Garros she had an injury that could get really worse, and that would have been extremely bad. That was definitely the right decision to stop, to heal, and to start working hard because she was able after that to do the necessary work in order to get fit."Now we're more in a virtuous circle than a vicious one. You have to start that virtuous circle by being fit, then everything goes better."For a daily dose of the best of the breaking news and exclusive content from Wide World of Sports, subscribe to our newsletter by clicking here!