Spoiler:
Following that match, Argentina's Francisco Cerundolo beat Alejandro Davidovich Fokina 6-3, 7-5 to earn defending champion Team World an early 2-0 lead in the first-to-13 event.
Cerundolo completed a day-session sweep for his team with a roller-coaster win against Spain's Davidovich Fokina. Like Shelton, Cerundolo's game plan was also built around his big forehand. While the Argentine was less dominant on serve — he won 54 per cent of his first-serve points to Shelton's 84 per cent — he constantly kept his opponent under pressure with power and consistency off the ground.
A battling performance from Davidovich Fokina kept the scoreline close, with the Spaniard denying his opponent's attempts to serve out the opening set at 5-1 and the second at 5-4. In both cases, Cerundolo responded brilliantly. With Team Europe sensing a comeback late in the match, the Argentine used drop shots on consecutive points to break from deuce at 5-5, then served out the victory from 15/30 at the second time of asking.
The Argentine said he felt McEnroe's influence from the sideline, winning 12 points in the frontcourt.
"To be honest, I went to the net a lot of times. I never go," he said. "Probably because I saw John there and I tried to copy him a little bit and I made some good points. I hope he's happy with my volleys, at least a little bit," he joked.
Team World has never held a lead after Day 1 at Laver Cup. With one evening win, they will finish Friday with an advantage on the scoreboard.
Friday's evening session in Vancouver will see home favourite Felix Auger-Aliassime take on Team Europe's Gael Monfils before Americans Tommy Paul and Frances Tiafoe play Fils and Andrey Rublev in doubles.
"We've got some new blood. There's a lot of energy," McEnroe said after Cerundolo's victory. "I think we've always had the team spirit, but there's a great team feeling. And obviously we've come in guns blazing. It's great to have a lead.
"For Francisco to win, it means a lot because we have a predominantly American team. But he did his thing."
The first team to reach 13 points will win the Laver Cup. One point is awarded for each victory on Friday, two points for each win on Saturday, and three for each win on Sunday.