Russian Daniil Medvedev overtook Rafael Nadal and moved into No 2 in the ATP rankings on Monday.
And for the first time since the computerized rankings began in August 1973, there is no American man in the top 30.
Novak Djokovic remained No 1, extending his all-time record to 320 weeks. Medvedev slid in behind him after Spain's Nadal fell to eventual champion Alexander Zverev of Germany in the quarterfinals of the Mutua Madrid Open last week.
A first-round loss in Madrid by Taylor Fritz, the highest-ranked American, dropped him one spot to No 31 in the rankings. John Isner, who was defeated in the quarterfinals in Spain, climbed five spots to No 34.
In the most recent rankings, Nadal dropped to No 3, and the next five spots remained unchanged with Austrian Dominic Thiem at No 4, followed by Stefanos Tsitsipas of Greece, Zverev, Russian Andrey Rublev and Roger Federer of Switzerland.
Italian Matteo Berrettini and Argentine Diego Schwartzman flipped places, with Berrettini moving from No 10 to 9 after reaching the Madrid final.