Davidovich Fokina powers into Monte Carlo semi-finals for second time
World number 42 Davidovich Fokina, who was runner-up at the tournament in 2022 to Stefanos Tsitsipas, swatted aside Australia's Popyrin 6-3, 6-2 in the last eight.
He will face either Carlos Alcaraz or French rising star Arthur Fils in the last four on Saturday.
Davidovich Fokina was full of confidence after dumping out British fifth seed Jack Draper in the last 16, but had to wait to take control of the first set.
Popyrin staved off three break points in a marathon sixth game to level at 3-3, but Davidovich Fokina did seal a break two games later and then confidently served out for a one-set lead.
Davidovich Fokina extended his run of successive games to seven as he raced into a 4-0 advantage in the second set, before securing victory on his second match point as Popyrin ballooned a backhand long.
Also later on Friday, Grigor Dimitrov faces Alex de Minaur and three-time champion Stefanos Tsitsipas plays Lorenzo Musetti in the quarter-finals.