Roger Federer and Rafael Nadal played as doubles partners for the first time on the second day of the inaugural Laver Cup in Prague.
Swiss Federer and Spaniard Nadal, who have won a combined 35 Grand Slam titles, are part of a Europe side that play a World team over three days.
They beat Americans Sam Querrey and Jack Sock 6-4 1-6 (10-5) to give Team Europe a 9-3 lead.
The winner is the first to 13 points, with 12 points available on Sunday.
Team Europe’s players include world number four Alexander Zverev and seventh-ranked Dominic Thiem, while Nick Kyrgios and Denis Shapovalov, who impressed at the US Open, have represented Team World.
None of the matches played are part of the ATP Tour but they have attracted healthy crowds in the Czech capital.