It was D-Day down under.

Americans got off to an awful start on the opening day at the Australian Open on Monday, with 12 players on both the men’s and women’s side falling, including top-seeded Americans Venus Williams and Jack Sock.

But perhaps the biggest — and most embarrassing — shocker belonged to CoCo Vandeweghe, who ripped apart chair umpire Fergus Murphy over bananas and opponent Timea Babos before bowing out, 7-6 (7-4), 6-2.

Vandeweghe entered Monday with a career-high ranking (ninth) and coming off her best calendar season last year, but once again fell victim to her own combustibility. First, she was hit with a time violation for waiting too long for a banana to be brought to the court between sets, which resulted in a point penalty to start the second set. Vandeweghe whined to Murphy between sets after she refused to take the court without eating a banana first.

”I was just trying to wait for what I asked for to come, and the chair umpire deemed that it wasn’t a good enough reason,” she said.

But it only got worse for Vandeweghe. While she normally plays with much emotion, she was hit with another point penalty for unsportsmanlike conduct while trailing 1-5 in the second set. After throwing her racket on the court, Vandeweghe appeared to scream obscenities toward Babos.

Vandeweghe attributed her poor form to the flu, which she revealed had her bedridden the last four days.

While that was the most embarrassing moment from a miserable Monday, which saw the US women go a shocking 1-9 in play, the carnage started when 13th-seeded Sloane Stephens became the first of three American US Open semifinalists to fall within hours in Melbourne, where she lost in three sets, 2-6, 7-6 (2), 6-2, to Zhang Shuai.

It’s been quite the fall for Stephens, who remains winless in eight consecutive matches since winning the US Open title in September. Some, like Chris Evert, have questioned Stephens’ commitment after winning her first Slam, and that discussion certainly isn’t going to disappear anytime soon.

Shortly after Stephens, it was last year’s Australian Open runner-up, Venus Williams, to fall to upstart Belinda Bencic, 6-3, 7-4. Williams had 26 unforced errors against the 20-year-old Bencic, who reached No. 7 in the world in 2016, before injuries plagued her play much of the last two years. Now ranked No. 78, Bencic is back in action after missing the last five months with left wrist surgery and earned some praise from Williams.

”I don’t think I played a bad match. She just played above and beyond,” Williams said. ”I just have to give her credit for that.”

Upstart Americans CiCi Bellis and Sofia Kenin also tapped out on the first day to add to the shocking 1-9 mark.

On the men’s side, highest-seeded American Jack Sock lost 6-1, 7-6 (4), 5-7, 6-3 to Yuichi Sugita while No. 16 John Isner lost to 76th-ranked Australian Matthew Ebden. Ryan Harrison and Mackenzie McDonald helped the American men go 2-3 on Monday.

The lone American female winner, Nicole Gibbs, ended the eight-straight-losses streak when she beat Viktoriya Tomova 6-1, 6-1.

”We were talking about it in the locker room and some of them were ribbing me that I had to carry the flag for us,” Gibbs said. ”It was a tough day, and this is a tough sport. This isn’t an indication of anything except we have a lot of depth and we had a bad day.”