Carlos Alcaraz was forced to withdraw from the quarterfinals of the Paris Masters Friday.

On Saturday, he announced the extent of his injury, which will keep him out about six weeks.

Carlos Alcaraz during match

Carlos Alcaraz of Spain against Holger Vitus Nodskov Rune of Denmark in the quarterfinals of the Rolex Paris Masters Nov. 4, 2022, in Paris.  (Quality Sport Images/Getty Images)

"After my withdrawal yesterday and having been evaluated by my medical team … unfortunately this is the result of my injury: an internal oblique muscle tear in the left abdominal wall with an estimated recovery time of six weeks," Alcaraz tweeted Saturday afternoon.

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The injury will force Alcaraz to miss the ATP Finals and the Davis Cup.

"It is tough and painful for me to miss these two events, which are so important to me, but all I can do is be positive and focus on my recovery," he said in a follow-up tweet.

Carlos Alcaraz salutes crowd

Carlos Alcaraz of Spain celebrates winning the third set tiebreak against Casper Ruud of Norway during their men’s singles finals match of the 2022 U.S. Open at USTA Billie Jean King National Tennis Center Sept. 11, 2022, in the Flushing neighborhood of the Queens borough of New York City. (Elsa/Getty Images)

The Australian Open begins Jan. 16. A six-week recovery timeline would have him ready before the new year, but it's no guarantee.

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Alcaraz is ranked No. 1 in the world at just 19 years of age, the youngest player to ever take the top spot.

He won his first two matches at the Paris Masters in straight sets but retired in the tiebreaker of the second set on Friday after losing the first.

Carlos Alcaraz getting looked at by doctor

Carlos Alcaraz of Spain receives treatment after being injured in a match against Holger Vitus Nodskov Rune of Denmark in the quarterfinals during of the Rolex Paris Masters Nov. 4, 2022, in Paris. (Quality Sport Images/Getty Images)

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He went 57-13 this year, winning the U.S. Open and making it to the quarterfinals of the French Open.