US Open

Daniil Medvedev could use a refresher course in tennis etiquette after twice flying off the handle at the US Open Thursday night.

The tennis star first lost his cool after he blew several match points — one by double-faulting —  in the third set of his second-round match against Christopher O’Connell in Louis Armstrong Stadium.

O’Connell went on to win the set, prompting an angry Medvedev to lash out at a camera person filming him during a break.

In the fourth set, Medvedev acted up again, yelling at crowd members chatting and walking back to their seats as he was about to serve. He screamed, “Can you shut up guys? Are you stupid or what?”

The audience booed Medvedev, but he still went on to victory, beating O’Connell 6-2, 6-2, 6-7 6-2.

Barack and Michelle Obama cheered on Novak Djokovic from the front row of the tennis superstar's US Open match Monday night ... an interesting sight -- considering the trio couldn't have been more in disagreement over the COVID vaccine for the past few years.

No. 44 and his wife were spotted clapping after most of the Joker's points in his dominant win over Alexandre Muller at Arthur Ashe Stadium in New York.

The match marked the first time Djokovic was able to participate in the famous tournament since 2021 -- as he wasn't allowed to travel to the U.S. last year due to his unwillingness to get the COVID vax.

Of course, the Obamas have staunchly urged people to get the jab since it became available years ago -- even sharing videos of them receiving it back in 2021.

Seems all three were able to put their differences aside Monday night, however ... 'cause it was all smiles from each party throughout the evening.

Hours before Djokovic's big win, the Obamas took in Coco Gauff's match against Laura Siegemund ... and the U.S. star couldn't have been more thrilled about it.

Despite a frustrating match where she argued with officials over the way Siegemund was taking extended breaks between points ... Gauff said her whole mood changed when she got to meet with the Obamas afterward.

"I was like, 'Oh, my God,'" Gauff said, starstruck after their meetup. "I haven't soaked it in because I literally just walked in here. I think I'm going to never forget that moment for the rest of my life. I went from being really upset after a win to, like, being really happy."

The best tennis player in the world is no match for Jimmy Butler -- the NBA superstar proved he's got serious skills on more courts than just the hardwood ... by scoring a point off Carlos Alcaraz during a U.S. Open charity event!!

The Miami Heat hooper was serving as an honorary ball boy for the Spanish star's contest against Frances Tiafoe at the Stars of the Open at Louis Armstrong Stadium on Wednesday ... when all of a sudden, he decided to step in and show off his tennis game.

Okay, so Butler might not be the next Federer ... but he certainly held his own as he rallied with the No. 1-ranked Alcaraz, who was obviously taking it easy on the six-time All-Star.

At one point, Butler asked Alcaraz to hit him with a fast serve so he could prove he could successfully return ... but didn't get his wish, as his opponent put in about 5% power on his attempt.

But, it was Jimmy Buckets who got the crowd roaring by the end of the point ... sneaking a shot past Alcaraz to come out on top!!