Italy's Matteo Berrettini beat Felix Auger-Aliassime of Canada in a match tie-break as Team Europe won the opening two ties at the Laver Cup.
World number seven Berrettini came back to win 6-7 (3-7) 7-5 10-8 against Team World's Auger-Aliassime in Boston.
Earlier, Norway's Casper Ruud defeated American Reilly Opelka 6-3 7-6 (7-4).
It is the fourth edition of the Laver Cup, which sees six men's players from Team Europe and Team World contest a series of singles and doubles matches.
World number 11 Auger-Aliassime, 21, was unable to take his first seven set points in an entertaining 80-minute opening set - which he was eventually able to clinch in a tie-break.