No. 11 seed Karen Khachanov and No. 14 seed Cristian Garin were ousted on the first day of Internazionali BNL d'Italia on clay courts in Rome.
Khachanov, of Russia, was defeated 6-3, 3-6, 6-1 by Casper Ruud of Norway, while Garin, of Chile, was eliminated 6-4, 6-4 by Borna Coric of Croatia as the ATP Tour moved to clay courts following the completion of the U.S. Open on Sunday.
Rudd had 17 break-point chances while taking control of his match, while Coric continues to play well after advancing to the quarterfinals of the U.S. Open.
Also eliminated in Monday's first round was No. 16 seed Felix Auger-Aliassime of Canada, who was defeated 6-4, 7-5 by Filip Krajinovic of Serbia. Krajinovic lost just three of his 30 first-serve points.
No. 15 seed Grigor Dimitrov of Bulgaria avoided being upset when he defeated wild card Gianluca Mager of Italy 7-5, 6-1.
Two wild cards advanced to the second round, both from Italy, as Stefano Travaglia defeated Taylor Fritz 6-4, 7-6 (4) and Jannik Sinner defeated Benoit Paire of France 6-2, 6-1.
Japan's Kei Nishikori, who has not won a match since the 2019 U.S, Open was a 6-4, 7-6 (3) winner in the first round against Albert Ramos-Vinolas of Spain. Nishikori had elbow surgery in October.
"Very happy to win. I think winning is most important for now," Nishikori said. "I need to get a lot of confidence. It's been a long time since the U.S. Open last year. Happy to go through. It wasn't maybe perfect yet, but hopefully one by one I'll get better."
Marin Cilic of Croatia defeated Alexander Bublik of Kazakhstan 6-7 (4), 6-2, 6-4 to advance to the second round. Dimitrov and Cilic have advanced to the semifinals of the tournament, with Cilic getting there two years ago.
Ugo Humbert of France earned a 6-3, 7-6 (5) victory over two-time Grand Slam finalist Kevin Anderson of South Africa.
Many of the top seeds in the tournament are still awaiting their first opponent after receiving a bye in the first round.
Novak Djokovic of Serbia is the top seed, and Rafael Nadal of Spain is No. 2. He opted out of the U.S. Open because of coronavirus concerns. Stefanos Tsitsipas of Greece is the No. 3 seed, while Matteo Berrettini of Italy is No. 4.
Nadal is a nine-time champion in Rome.
--Field Level Media