US Open at a glance - Day two:

Headlines

+ Nadal breezes past Australian John Millman to reach second round

+ Top-seeded defending champion Osaka hit by nerves but advances

+ Austrian fourth seed Thiem ousted by Italy's Thomas Fabbiano

+ Eighth-seeded Tsitsipas, Russian ninth seed Karen Khachanov and 10th seed Bautista Agut also exit Nadal's half of the draw

+ Halep advances in three sets over US cancer-conqueror Nicole Gibbs

Top results

Rafael Nadal (ESP x2) bt John Millman (AUS) 6-3, 6-2, 6-2

Naomi Osaka (JPN x1) bt Anna Blinkova (RUS) 6-4, 6-7 (5/7), 6-2

Simona Halep (ROU x4) bt Nicole Gibbs (USA) 6-3, 3-6, 6-2

Thomas Fabbiano (ITA) bt Dominic Thiem (AUT x4) 6-4, 3-6, 6-3, 6-2

Andrey Rublev (RUS) bt Stefanos Tsitsipas (GRE x8) 6-4, 6-7 (5/7), 7-6 (9/7), 7-5

Sidelines

Karlovic oldie but goodie

Croatia's Ivo Karlovic was the oldest US Open men's main draw player since 1977 but retired Tuesday in his first-round match / © GETTY IMAGES NORTH AMERICA/AFP

-- Croatia's Ivo Karlovic, 40, became the oldest US Open men's singles player since Ken Rosewall reached the third round in 1977 at age 42 when he faced 21-year-old Frances Tiafoe. World number 79 Karlovic, whose best US Open showing was a 2016 run to the last 16, retired to hand the American a 6-2, 6-3, 1-2 triumph in 64 minutes.

Teens Coco, Potapova meet

-- It was the youngest matchup at the US Open with 15-year-old US wildcard Cori "Coco" Gauff beating 18-year-old Russian Anastasia Potapova 3-6, 6-2, 6-4. Gauff, who became a Wimbledon sensation with a run to the fourth round that included beating idol Venus Williams, is the first player under 16 to win a US Open match since CiCi Bellis five years ago. Next she will next meet Hungarian qualifier Timea Babos with top-ranked defending champion Naomi Osaka a possible third-round foe.

Ramos forgotten, not gone

-- Carlos Ramos, the umpire called a "liar" and a "thief" by Serena Williams in her outburst at last year's US Open final, was barred from handling her matches this year or those of her sister Venus. Ramos awarded a penalty game to eventual champion Naomi Osaka for a third code violation. Asked about him on Monday, Williams said, "I don't know who that is." While forgotten, Ramos is not gone. He worked a court-eight match Monday between France's Pierre-Hugues Herbert and Australian Alex de Minaur and returned to Arthur Ashe Stadium on Tuesday to officiate Austrian fourth seed Dominic Thiem's loss to Italy's Thomas Fabbiano.

Even a loser can win

-- Those players who lose in the qualifying finals but get into the main draw when a player drops out, the lucky losers, are common enough. But it's not every day they play each other in the first round of a Grand Slam, although that's what happened Tuesday when Belgian Kirsten Flipkens beat China's Wang Xiyu 3-6, 6-2, 6-2. Flipkens next faces Canada's Bianca Andreescu.

Who's saying what

Spain's Garbine Muguruza serves in a loss to Alison Riske on Tuesday at the US Open / © AFP

"I remember not even that long ago, a few years ago, it was different. You had a difference between the top players and little not top players. Now you feel like if you're not 100 percent every day you have matches like today, opponents play just great... Everybody is a threat."

-- Two-time Grand Slam winner Garbine Muguruza of Spain on the rise in parity in women's tennis after her first-round loss

"I loved it. These Canadians are wilding. They're coming everywhere. It's really nice to see all of the Canadians cheering me on in different cities."

-- Canadian teen Bianca Andreescu, who has attracted loud and passionate supporters from her homeland to matches in Toronto, Cincinnati and now New York after a first-round US Open victory

"This chair umpire, he has something against me. I don't know why... "I feel like some of them have preferences when they are on the court."

-- Greek eighth seed Stefanos Tsitsipas after his fourth consecutive loss this month brought his second first-round Grand Slam exit in a row

Austrian fourth seed Dominic Thiem lost to Italy's Thomas Fabbiano in a first-round match Tuesday at the US Open / © AFP

"I got very tired and exhausted after two sets. I'm far away from 100 percent... It was not the real me there on the court."

-- Austrian fourth seed Dominic Thiem on not being his best at the US Open in his Tuesday loss to Italy's Thomas Fabbiano

"I've always known that I'm a fighter. but to be through the journey I've been through over the past few months, to land myself on Armstrong playing against one of the best in the game, and going the distance, I think that really just reinforces it for me. I'm going to take a lot of inspiration from this, try to carry it forward into what's left in my year and my tennis career."

-- US lucky loser Nicole Gibbs, who underwent surgery for salivary gland cancer in May and battled back just to play in the US Open