Cameron Norrie was beaten in straight sets by 15th seed Karen Khachanov in the first round of the Monte Carlo Masters.
Norrie fought hard in a match lasting two hours and 25 minutes but went down 7-5 7-6 (7-3) to the Russian.
The British number one had two set points to level the match at one set all before Khachanov came through in the tie-break.
Fellow Briton Dan Evans was beaten 6-1 6-4 by Austria’s Sebastian Ofner.
Norrie broke at the first time of asking to go 2-0 up in the first set but Khachanov immediately broke back.
The Russian secured the decisive break, the last of five in opening set, in the 11th game and broke again to start the second set.
Norrie responded in the next game and broke again for a 5-3 lead but could not serve out the set.
He had another chance to break and force a deciding set but two set points went begging and the momentum was with Khachanov as he stormed ahead in the tie-break.
Norrie managed to save two match points but Khachanov converted the third and advances to play Argentina’s Francisco Cerundolo in the second round.
Meanwhile, world number 50 Evans, playing his second match of the season on clay, lost a 70-minute match to Ofner.
Evans had two break points in the opening game but could not convert and went on to lose the next four games.
He dropped serve early in the second set and, despite a late wobble from Ofner, could not force a decider.
British number three Evans has not won back-to-back singles matches on the ATP Tour this year.
The event in Monte Carlo is one of the nine Masters tournaments, which are the biggest men’s tour events outside of the four Grand Slams.
Jack Draper takes on Poland’s 10th seed Hubert Hurkacz on Tuesday.