ATP World Tour Finals 2021 Results: Novak Djokovic Win Headlines Monday's Scores

Novak Djokovic is seeking his sixth career title at the ATP World Tour Finals, but it won't be an easy path with seven other top competitors vying for the top prize.

Djokovic began round-robin play in Turin, Italy, with Monday's match against Casper Ruud, while Stefanos Tsitsipas and Andrey Rublev rounded out the Green Group. Though the tournament is not single elimination, the stakes of each match are high with only two of the four advancing to the semifinals.

Alexander Zverev and defending champion Daniil Medvedev lead the Red Group after strong showings on Day 1. Here is the latest in Day 2 from the year-end tournament:

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Monday Scores

No. 1 Novak Djokovic def. No. 8 Casper Ruud; 7-6 (4), 6-2

No. 5 Andrey Rublev def. No. 4 Stefanos Tsitsipas; 6-4, 6-4

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Novak Djokovic Overcomes Slow Start in Victory

There was a major difference in experience entering the match, as Ruud was competing in his first ATP World Tour Final while Djokovic is a yearly fixture at this event. Of course, the No. 1 player in the world hasn't won since 2015, so nothing is guaranteed.

Ruud showed his skill from the very beginning, forcing a break on the first game of the match before going up 2-0 in the opening set.

Then again, Djokovic found ways to impress even when he didn't win the point:

The veteran found his footing later in the set, but Ruud refused to back down while forcing long rallies and saving multiple set points to force a tiebreak.

Djokovic finally escaped with the 7-6 set victory:

It was a much different story in the second set as the top seed played like it in a dominant 6-2 showing.

Djokovic won an incredible 16 of 19 service points in the second set to go with two breaks. The Serbian was nearly flawless with his serve throughout the match, going 35-of-39 on first-serve points with 10 aces and zero double-faults.

It was enough to secure a straight-set victory that put him one step closer to the knockout stage.

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Andrey Rublev Levels All-Time Series

Entering Monday, Tsitsipas had a slim 4-3 head-to-head advantage over Rublev. Most recently, the Greek prevailed at the Rolex Monte-Carlo Masters in April.

Rublev gained a measure of revenge in Turin.

Tsitsipas narrowly avoided a major setback early in the match as he saved three break-point chances in the opening game of the first set.

He wasn't quite so lucky when serving at 2-2 as he fell behind 15-40 and allowed Rublev to get into the driver's seat. That was the opening the Russian needed to eventually claim the set.

The action followed almost exactly the same blueprint in the second set. Rublev had a break point in the first game he couldn't fully capitalize on but then broke Tsitsipas in the fifth game to move ahead 3-2.

Tsitsipas was unable to wrest control back and fell in straight sets.

Rublev was dominant on serve, piling up nine aces and winning 90 percent of his first-service points. He was far less effective with his second serve (6-of-19), yet it didn't matter toward the outcome.