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Carlos Alcaraz is two wins from guaranteeing he will be the youngest World No. 1 in Pepperstone ATP Rankings history.

Will Alcaraz Or Ruud Clinch World No. 1 On Friday At US Open?

Nadal also in contention

The battle for the No. 1 spot in the Pepperstone ATP Rankings has been one of the most interesting storylines of this US Open. On Friday, it could be decided.

If Casper Ruud loses to Karen Khachanov in the first semi-final and Carlos Alcaraz falls to Frances Tiafoe, Rafael Nadal will return to World No. 1 for the ninth time. If Alcaraz or Ruud win, Nadal will be eliminated from contention.

If Alcaraz and Ruud both advance to the final, everything will be at stake on Sunday. The Spaniard and Norwegian would be playing for their first Grand Slam trophy and World No. 1. If one of them wins his semi-final and the other doesn't, the player who reaches the final will be World No. 1 on Monday.

Pepperstone ATP Live Rankings Round By Round

 Player  R4  QF  SF  F  Title
 Rafael Nadal  5,810  -  -  -  -
 Carlos Alcaraz  -  -  5,460  5,940  6,740
 Casper Ruud  -  -  5,370  5,850  6,650

After 3:30 a.m. on Thursday morning following his epic five-set quarter-final thriller against Jannik Sinner, Alcaraz was asked by a reporter if his opportunity to reach World No. 1 had entered his mind during the match.

"I just was thinking about the match, not the ranking or results or stuff," Alcaraz said. "I just try to be focussed, try to put my best in every shot, in every game."

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Alcaraz is trying to become the youngest World No. 1 in Pepperstone ATP Rankings history, while Ruud can become the first player from Norway to accomplish the feat.

Entering the semi-finals, Rafael Nadal is No. 1 in the Pepperstone ATP Live Rankings, Alcaraz is No. 2 and Ruud is No. 3. That means Alcaraz and Ruud will reach career-high rankings regardless of their performance the rest of the tournament.