Only four of Monday's 13 scheduled singles matches were completed before rain halted play on the opening day of the Rolex Monte Carlo Masters in Monaco.
Spain's Alejandro Davidovich Fokina, Australia's John Millman and Russia's Aslan Karatsev all won in straight sets, while American Tommy Paul was leading 4-1 when Spain's Pedro Martinez was forced to retire.
Karatsev defeated Italy's Lorenzo Musetti 6-3, 6-4 in a match interrupted by a four-hour rain delay. He saved all four break points he faced and fired 23 winners.
"It was a really tough match (for) my first match of the season on clay (with) tough weather conditions," said Karatsev. "We started in the morning (and) I started pretty well, I broke him and then the court was getting heavy, the ball was heavy. It is tough to play against him. (He is) really fit, (he) runs a lot and gives everything back, so you have to build the point by yourself and close the point by yourself."
Kartasev will face No. 4 seed Stefanos Tsitsipas of Greece in the second round, their first-ever meeting.
Davidovich Fokina saved six of the eight break points he faced in a 6-4, 7-6 (3) win over Australia's Alex De Minaur. His second-round opponent will be No. 8 seed Matteo Berrettini of Italy.
Millman broke Frenchman Ugo Humbert's serve four times in a 6-3, 6-3 victory. Millman saved four of five break points.
Five matches were in progress on the clay courts when the weather stopped play for a second and final time.
Felix Auger-Aliassime of Canada leads 4-2 against No. 16 seed Cristian Garin of Chile. Britain's Daniel Evans took the first set, 6-3, against 2019 Monte Carlo runner-up Dusan Lajovic of Serbia. Miami Open winner and No. 13 seed Hubert Hurkacz of Poland leads Italy's Thomas Fabbiano, 6-3, 0-1. France's Jeremy Chardy is up 5-4 against Alexander Bublik of Kazakhstan. Monaco's Lucas Catarino is up 7-6 (3), 3-2 against Spain's Salvatore Caruso.
Millman's second-round opponent will be the winner between Auger-Aliassime and Garin.
Those matches will resume Tuesday. Also scheduled to play is defending champion and No. 15 seed Fabio Fognini of Italy, whose first-round opponent is Miomir Kecmanovic of Serbia.
--Field Level Media