Anderson and Sock recover from a set down in Chicago to pull back point for Team World
Laver Cup: Federer and Djokovic defeated in doubles but Europe hold lead
Kevin Anderson and Jack Sock spoiled the doubles debut of Roger Federer and Novak Djokovic but Team Europe still led Team World 3-1 after the first day of the 2018 Laver Cup.
Grigor Dimitrov, David Goffin and Kyle Edmund all won their opening singles matches on Friday to give Team Europe a commanding 3-0 lead going into the evening's final doubles match.
Team World's Sock and Anderson needed a tiebreaker to defeat the doubles dream team of Federer and Djokovic 6-7, 6-3, 10-6.
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Sock and Anderson won the tiebreaker after Federer double faulted to give Team World a key 5-4 lead.
Earlier in the day, Europe's Dimitrov cruised past Frances Tiafoe 6-1, 6-4, Goffin saved two match points to outlast Diego Schwartzman 6-4, 4-6, 11-9 and Edmund toppled Sock 6-4, 5-7, 10-6.
This is the second installment of the Laver Cup which has been dubbed the Ryder Cup of tennis - although it lacks the tradition of golf's premier team event.
The exhibition is taking place on US soil for the first time and features 12 of the world's top players squaring off against each other in a three-day showcase which wraps up Sunday in Chicago.
The format calls for shorter matches: if the players split sets, they go straight to a 10-point tiebreaker. On Saturday, wins will be worth two points each instead of one, and on Sunday each win is worth three points.
Dimitrov used his precision backhand to keep Tiafoe off balance as he closed out the match with his 10th and final ace. The Bulgarian hammered 27 winners to just seven for Tiafoe.
"It's pretty nice to play indoors - no sun, no wind," Dimitrov said. "When you get in a good rhythm you just want to follow it. I think today that's what I did."
Bjorn Borg's favoured Team Europe are trying to defend their crown against Team World which is captained by the John McEnroe.
Federer, Djokovic, Alexander Zverev, Dimitrov, Goffin and Edmund make up Team Europe. Federer played in the first Laver Cup but Djokovic is taking part for the first time.
Sock, Nick Kyrgios, John Isner, Tiafoe, Anderson and Schwartzman are representing Team World.
The event is named in honour of tennis legend Rod Laver, who won a record 200 singles titles, 11 grand slams and five Davis Cups for Australia.