Britain’s Andy Murray and Cameron Norrie are both beaten in the Rotterdam Open second round.
Murray, now ranked 123rd, had won his first tour-level match since August by beating Robin Haase on Monday.
However, fourth seed Rublev secured the match in one hour and 34 minutes.
British number three Cameron Norrie also lost to a Russian player, Karen Khachanov, who recorded a 6-2 6-2 victory in an hour and 14 minutes.
It was the first meeting between world number 21 Khachanov, conqueror of eighth seed Stan Wawrinka in the opening round, and qualifier Norrie, ranked 65.
Murray triumphed over a 19-year-old Rublev in their only previous meeting at the 2017 Australian Open, but was deemed the underdog on Wednesday.
The opening set was well contested, before Rublev gained a break in the 11th game following a Murray double fault.
After Murray was unable to convert two break points to take the opening set to a tie-break, Rublev raced away with the second, winning five successive games to book his place in the quarter-finals against David Goffin or Jeremy Chardy.
Murray, who says he plans to play in Dubai in a couple of weeks and then Miami at the end of the month, smashed his racquet in anger during the defeat.
He said: “I did some things quite well in the first set, but when it mattered I didn’t play well.
“I lost my serve from 30-love up: I hit two double faults, and a bad forehand. To me that’s just not good enough. I felt in that moment at the end of the first set that I blew it a bit.
“I’m not used to making those errors in those moments and I’m finding that quite frustrating, and mentally finding myself looking back on those moments a little bit too much.”
Former world number one Murray, winner of the Rotterdam tournament in 2009, missed last month’s Australian Open after testing positive for coronavirus and lost in straight sets to Egor Gerasimov on his ATP Tour comeback in Montpellier last week.
Last month, three-time Grand Slam winner Murray, 33, reached the final of the ATP Challenger event in Biella, Italy, but lost 6-2 6-4 to Ukraine’s Illya Marchenko.
Meanwhile, the ATP has announced that prize money will be increased at lower-ranked tournaments as part of a financial support package amid the coronavirus pandemic.
ATP 250 and ATP 500 events will see winnings rise from 50% of pre-Covid totals to 80% and 60% respectively up until Wimbledon, which is due to take place from 28 June to 11 July.
The extra £3.72m will come from money that ordinarily goes to the top 12 players at the end of the season.
