Sport without fans really hasn't been the same. But tennis without a live audience? That's probably the worst of the lot.
There is no piped in crowd noise and not even any communication among teammates; just two players in silent empty stadiums, the echo from each shot and squeak from every shuffle of the shoes amplified even louder. While atmosphere has inevitably suffered across all sports, tennis has been especially sterile.
So the return of spectators for the Australian Open, albeit at a limited capacity, has been a welcome sight. A live crowd has always played its part in the entertainment and drama of a tennis match, but for most of the first three days at Melbourne Park, there wasn't all that much for them to sink their teeth into.
That all changed on Wednesday evening and it should come as no surprise that the player to provide the spark was the sport's most natural showman.
Nick Kyrgios may have his detractors but boy can he whip a crowd into a frenzy. There were the standard theatrics – a smashed racquet, rants at the umpire, and underarm serving – but it was his gritty, snatch-victory-from-the-jaws-of-defeat performance that really raised the roof.
Twice the Australian faced match point in the fourth set against French 29th seed Ugo Humbert, twice he held his nerve. He eventually came through 5-7, 6-4, 3-6, 7-6, 6-4 after three hours and 25 minutes, slumping to the court in victory as the fans inside the John Cain Arena went wild.
Every Grand Slam has a match that makes the tournament come alive, although that has been hard to discern in the absence of fans. This match was undoubtedly it for the 2021 Australian Open.
"Honestly, I don't know how I did that. I don't even know what to say, I'm lost for words. That is one of the craziest matches I've ever played," 25-year-old Kyrgios said on court.
"It was a strange match, if you guys were inside my head, there were some dark thoughts in there.
"It's my career, I live to fight another day and hopefully I can continue to play tennis in front of you guys," he added, to another huge round of applause from the crowd.
Kyrgios' reward is a third round tie against third seed and reigning US Open champion Dominic Thiem, who long had his feet up after rattling through his second round assignment against Germany's Dominik Koepfer in just one hour and 39 minutes earlier in the day.
"He's one of the best players in the world," said Kyrgios, who first is back in action on Thursday in the doubles. "I'm not even going to think about that."
Win or lose for Kyrgios, it promises to be another spectacle and another reminder of the immense value a stadium crowd brings to live sport.
Thiem indeed knows a thing or two about big matches and raucous crowds at the Australian Open having reached last year's final, where he went down after a five-set thriller against Novak Djokovic.
That victory handed Djokovic a record-extending eighth Melbourne Park title and the top seed maintained his bid for a ninth with a testing four-set win over American Frances Tiafoe.
"I thought we both played on a pretty high level. I mean, he pushed me to the very limit," the 33-year-old Serb said after his 6-3, 6-7, 7-6, 6-3 win inside Rod Laver Arena.
"Just overall challenging conditions. It was very hot, we had long exchanges. It was a tough match, and I'm really glad to overcome such a battle."
Alongside Djokovic, there were only two other players in the men's draw to have tasted success at the Australian Open, and while Rafael Nadal continues his campaign against American Michael Mmoh on Thursday, Stan Wawrinka's journey came to an end in the most dramatic of circumstances.
The 2014 champion battled back from dropping the first two sets to Hungary's Marton Fucsovics only to lose the deciding fifth in a tense tie-break as the Swiss exited the tournament 7-5, 6-1, 4-6, 2-6, 7-6.
"Not the best level for me, but again, I was fighting, I had some chances to finish the match," said Wawrinka, who squandered three match points. "From 6-1 [in the tiebreak] I started to hesitate a little bit the way I was playing.
"I wanted to put the ball maybe too much in and I'm not going completely for my shots and that's when I started to miss a little bit and it helped him to come back in the match."