2021 U.S. Open Day 2: Novak Djokovic, Ash Barty Survive Early Tests to Book Spots in Round 2

(Photo : ANGELA WEISS/AFP via Getty Images) Serbia's Novak Djokovic eyes the ball during his 2021 US Open Tennis tournament men's singles first round match against Denmark's Holger Rune at the USTA Billie Jean King National Tennis Center in New York, on August 31, 2021.

Novak Djokovic's quest for a historic Calendar Slam remained right on track after securing a nervy four-set win over Danish teenager Holger Vitus Nodskov Rune in the first round of the 2021 U.S. Open. The world no. 1 needed two hours and 15 minutes to record the 6-1, 6-7 (5), 6-2, 6-1 win at the Arthur Ashe Stadium on Tuesday evening.

It looked like it would be an easy day in the office for Djokovic after he took the first set in just 26 minutes. Rune battled back, however, pushing the second set into a tie-break before eventually winning it 7-5 to level the contest at a set apiece.

THE CROWD IS ON THEIR FEET

Holger Rune wins the second set over Novak Djokovic in a tiebreak. #USOpen pic.twitter.com/x2s9hu1GEP
— US Open Tennis (@usopen) September 1, 2021

Djokovic improves first-round record at U.S. Open to 16-0

However, Rune's giant-killing plans were dashed as he suddenly suffered from cramps in the final two sets. Djokovic took full advantage of the Danish teen's misfortune, winning 12 of the next 15 games to improve his first-round record at Flushing Meadows to 16-0.

Next up for Djokovic is a second-round clash with Tallon Griekspoor. On Tuesday, the Dutchman produced a shock result, recording a first-round upset over big-hitting German Jan-Lennard Struff in a five-set thriller. Griekspoor needed three hours and 38 minutes to secure the stunning 2-6, 7-6(3), 4-6, 6-4, 7-5 victory and forge a dream showdown with Djokovic.

Djokovic paid tribute to Rune after their encounter, telling the 18-year-old that he earned not only the Serb's respect but also those who watched their contest. Djokovic finished the match with 55 winners and just 30 unforced errors.

Barty defeats Zvonareva in tense match

Also advancing to the second round was fellow top seed Ash Barty. The Australian overcame a second-set hiccup to defeat former U.S. Open finalist Vera Zvonareva in straight sets, 6-1, 7-6 (9-7). Barty was in fine form, blasting 11 aces and hitting 31 clean winners against her Russian opponent.

However, the match was engulfed in controversy when the electronic line calling system malfunctioned in the early stages of the second set. Barty asked the chair umpire if they could use human judges instead, but the umpire denied her request. Barty seemed to lose focus after that incident as she dropped serve with a double-fault while trying to finish the contest at 5-4.

Barty came close to losing the second set in a tie break, with Zvonareva grabbing a set point opportunity. Barty held her nerve, though, as she saved that set point before eventually winning the tie-breaker 9-7.

This was Barty's first match at Flushing Meadows in two years after sitting out last year's event due to the COVID-19 pandemic. She will next play Danish teenager Clara Tauson on Friday for a spot in the Round of 32.