ICYMI: What happened overnight at Australian Open

MELBOURNE – Good news, American tennis fans. It was a great day for the U.S. at the Australian Open. Yes, while you slept, America won. (And won and won and won.)
In fact, 13 Yanks advanced to round two here, marking one of the best single-day performances for the U.S. at a Grand Slam in recent memory. Here's what you missed on Day 2 in Melbourne, where tennis is seemingly happening in the future:
Oh, America! Whoever said 13 was an unlucky number? Serena and Venus Williams led a red, white and blue-tinged charge at Melbourne Park on Tuesday, which also included wins for No. 19 seed John Isner and highly-touted up-and-comer Madison Keys.
Steve Johnson, Nicole Gibbs, CoCo Vandeweghe, Donald Young, Lauren Davis, Irina Falconi, Varvara Lepchenko and Madison Brengle were all victors in their first round bouts. Serena and Venus each dropped just four games in their respective matches, while Brengle scored one of the biggest upsets of the day, a three-set thriller against No. 13 seed Andrea Petkovic. More on Brengle later.
Djokovic feeling all better: That stomach flu that was bothering top seed Novak Djokovic in the lead-up to the Australian Open? No sign of it on Tuesday, when the world No. 1 swept by Aljaz Bedene 6-3, 6-2, 6-4.
"It's behind me," the Serb told reporters of the bug after his win. Djokovic's ouster from a year ago, defending champion Stan Wawrinka, also won, moving the two closer to a third straight showdown.
Azarenka, Wozniacki set for round 2 clash: It's rare that two former world No. 1s meet in the second round of a major, but that's what is set to happen on Thursday after both Victoria Azarenka and Caroline Wozniacki won their openers.
Azarenka, whose ranking has taken a hit due to injury, rolled by American Sloane Stephens to advance, while Wozniacki beat another American in youngster Taylor Townsend to assure the meeting, their eighth. "I know she's very dangerous," Azarenka said of Wozniacki, whom she's 3-4 against. "We always [have] some tough matches."
Brengle's upset, revelation: At 23, world No. 64 Brengle is having a breakout few months, making it into the main draw by direct entry for the first time in her career.
She made headlines by beating the well-liked Petkovic on Tuesday, then revealed that she had a surgery during the off-season to remove a spot of skin cancer on her leg. "I had a touch of skin cancer so had to have a chunk of my leg taken out," Brengle told reporters. "I didn't know I was making this trip until two or three weeks before I left. They also found a mass in my jaw that is a tumor, but it's not cancerous, so I'm leaving that for now."
Brengle is a Delaware native, and reached her first career final last week in Hobart. She plays compatriot Falconi next.
PHOTOS: Day 2 at the Australian Open