American teenage star Coco Gauff beat Czech Karolina Muchova 6-3, 6-4 to win the biggest title of her career at the Cincinnati Open on Sunday. Meanwhile, Novak Djokovic of Serbia extended his Masters 1000 record to 39 titles over world number one Carlos Alcaraz of Spain 5-7, 7-6(7), 7-6(4).

Gauff, 19, broke Muchova three times in the first set and served out the opener to love. 

Muchova committed 35 unforced errors in the match and badly missed a backhand down the line to hand Gauff the break and a 3-2 second-set lead. 

Gauff struggled to capitalize on three match points while serving at 5-2 thanks to some tentative groundstrokes, but she did not falter on her fourth chance as Muchova's return landed wide, handing Gauff the victory on her WTA 1000 final debut.

Muchova will rise to world top 10 next week for the first time despite the loss, and Gauff has maintained outstanding form on North American hard courts ahead of the U.S. Open, which is scheduled to take place in New York from August 28 to September 10.

Later on Sunday, Novak Djokovic downed Carlos Alcaraz in almost four hours to avenge his loss to the 20-year-old in the Wimbledon final only a month ago. 

With the victory, Djokovic now has 68 "Big Titles" under his belt, including wins in Grand Slams, ATP Finals, ATP Masters 1000 tournaments and the Olympics.

In the longest Masters 1000 final ever played and what Djokovic admitted to have been "one of the toughest" matches in his career, the 36-year-old had a sluggish start, finding himself one set and a break down in unpleasant humidity, and barely moving when Alcaraz hit a backhand winner to grab the opener.

The Spaniard grabbed a 4-2 second-set lead, but went on to commit four unforced errors to give a lifeline to the world number two, who saved a championship point and went on to force a deciding set after winning a 25-shot rally.

Djokovic broke first in the third set to lead 4-3 and expanded the lead, only to be levelled by Alcaraz 5-5, whose return went wide twice in the tiebreak to give the Serb his 95th career title.

The two players now have a 2-2 head-to-head record going into the U.S. Open, where the 23-time Grand Slam winner is eyeing a record-extending victory in men's tennis.

(With input from Reuters)