Nick Kyrgios says his opponents' coach and trainer threatened to fight him after he and countryman Thanasi Kokkinakis scored a shock upset in Friday's doubles action.
The Aussie underdogs stunned top seeds from Croatia Nikola Mektic and Mate Pavic 6-7 6-3 in front of a wild crowd at Kia Arena.
Kyrgios and Kokkinakis, who have both been eliminated from the singles draw, had a ball in front of some boisterous fans but their opponents weren't exactly thrilled with the atmosphere.
Taking to Twitter on Saturday, Kyrgios wrote: "Just letting you know after yesterday's chop fest in doubles my opponents coach and trainer proceeded to threaten to fight in the players gym.
"Tennis is a soft soft sport @TKokkinakis all because I moved and hit them with a tennis ball."
Kokkinakis replied to Kyrgios' tweet, writing: "(Laughing emojis) that was crazy!! Mans thought it was @ufc."
Speaking on Nine, former Aussie tennis star turned commentator Sam Groth shed more light on the situation.
"Thanasi actually messaged me as it was happening and said Nick got accosted in the locker room by Pavic's fitness trainer and (they) obviously weren't very happy," Groth said.
"They're the No 1 team in the world, the No 1 seeds going down against Thanasi and Nick.
"They didn't accept what was going on with the crowd, didn't accept what was going on with Nick and I think it's a little bit soft.
"To take it off the court into the locker room, and not even from the players. From someone from the team, it's not necessary."
Mektic and Pavic won gold at the Tokyo Olympics last year and were heavy favourites to win the Australian Open together — but that dream has been crushed.
The crowd erupted as Kyrgios and Kokkinakis took the lead after a tie-break in the first set of Friday's clas. Kia Arena was not subjected to 50 per cent capacity like Rod Laver, and it showed.
In an all-Aussie move during the opener, one man demanded the crowd's attention to do a shoey (drink a beer from his shoe), with his fellow fans more than eager to get behind the gentleman and cheer him on.
The rowdy atmosphere, however, frustrated Pavic, who had a heated argument with the chair umpire.
In the second set on his serve, Pavic said: "This is p***ing me off … don't let that happen."
Speaking in a press conference after the match, Pavic told news.com.au it was not the crowd but rather "something else" annoying him which he didn't want to disclose.
As for the atmosphere, Pavic channelled Daniil Medvedev, who took aim at the "low IQ" Melbourne crowd after beating Kyrgios on Thursday night and said: "They are pretty loud, obviously they cheer for Aussies. It wouldn't hurt them to show some respect to all opponents, to other players.
"We saw yesterday also with Medvedev how it was. That's how they are here, we're used to that. But like I said, it wouldn't hurt them to show some respect."
Mektic praised his Aussie rivals, adding: "The guys played really well. They're a nasty team to beat here and that's it."