NEW YORK (AFP) — Venus Williams battled bravely before bowing out of the US Open on her return to Grand Slam tennis on Monday as Melbourne champion Madison Keys suffered a shock first-round exit.

The second full day of action in New York saw all eyes turn to the Arthur Ashe Stadium’s night session, where the 45-year-old Williams lost in three sets to 11th seed Karolina Muchova.

Williams only returned to competitive tennis in July following a 16-month absence from the sport and had been granted a wild card into the main draw at Flushing Meadows.

But hopes of a fairytale run — 28 years after her debut in the tournament in 1997 — ended in a 6-3, 2-6, 6-1 loss to Muchova, who was not even born when Williams turned professional in 1994.

“I didn’t win today but I’m very proud of the way I played,” Williams said.

“I don’t think I’ve ever had a crowd on my side like that. I knew people around the world and around the United States were really rooting for me, and that felt great.”

Carlos Alcaraz unveiled a striking new hairstyle before giving Reilly Opelka the chop.

The 22-year-old arrived on Arthur Ashe Stadium sporting a severe military-style crew cut for his night match with the American.

While Alcaraz’s new look failed to impress some — close friend and fellow player Frances Tiafoe called it “terrible” — it did not distract the streamlined Spaniard from the task at hand as he motored to a 6-4, 7-5, 6-4 first-round victory over the 6ft 11in Opelka.

Alcaraz could not hide his delight with his performance against his big-serving opponent.

“Today was a really difficult one,” Alcaraz said.

“Reilly is a great, tough player. I couldn’t get the rhythm that I wanted to get but I’m just really happy with what I did today. I did a great performance today.”

Asked about his new look, Alcaraz smiled.

“I think I’ve got to ask the people if they like it or not,” he said, to cheers from the New York crowd. “I think they like it.”

Alcaraz, who won the first of his five Grand Slam singles titles at the US Open in 2022, took control with a break in the fifth game of the first set, retaining that advantage before serving out to love.

Also Monday, Australian Open winner Keys became the highest-ranked player to exit so far, the sixth seed losing to Mexico’s Renata Zarazua 6-7 (10/12), 7-6 (7/3), 7-5.

“Today was the first time in a while where my nerves really got the better of me and it kind of became a little bit paralyzing,” home hope Keys said.

“I was just slow, I wasn’t seeing things the way that I wanted to, which I feel like resulted in a lot of bad decisions and lazy footwork.”

Czech Republic’s Barbora Krejcikova bundled out rising Canadian star Victoria Mboko, defeating the teenager 6-3, 6-2.

Belgian 19th seed Elise Mertens ousted wild card Alyssa Ahn 6-1, 6-0 while Ukrainian 30th seed Dayana Yastremska exited in a 6-7 (5/7), 7-6 (7/5), 6-4 loss to Russia’s Anastasia Pavlyuchenkova.