John McEnroe and Bjorn Borg have filled the job since the tournament began, and it’s more than ceremonial.In the first three Laver Cups, the biggest names were the most famous players in tennis: Roger Federer (who helped create the tournament) played each year, Rafael Nadal played twice and Novak Djokovic played once.All are absent this year at the event in Boston, so while six Top 10 players are on board, the biggest names will be the most famous players in tennis circa 1980: the Team World captain, John McEnroe, and the Team Europe captain, Bjorn Borg, both returning for their fourth time.The Laver Cup brings a team sport format to tennis, and the captains have a role unlike almost any other in tennis.Captains recruit and select a team, build team spirit during practices, pick lineups according to the event’s quirky rules and provide in-match coaching.“There’s a lot to consider and a lot of tactics when making out the lineups, so in that sense the captain’s role is pretty important,” said Thomas Enqvist, vice captain of Team Europe.McEnroe takes his job seriously, but he downplays its importance. “It’s not the toughest job in the world,” he said with a laugh. “I show up at some cocktail parties and pick up balls at practiceThere is more to the job than that. Captains must persuade the top-ranked players, who are invited to the tournament based on their rankings, to participate. They also choose three lower-ranked players, called captain’s picks.“Before the first year, I had to call the players and explain the tournament,” Borg said, although having Federer’s backing made his job easier. For the captain’s picks, he added, “I’m watching so much tennis all year to see who fits the team, who may be in the best shape.”Federer, left, of Team Europe, with Borg, the team captain, at the 2018 Laver Cup.Clive Brunskill/Getty ImagesTeam Europe has had a huge edge in singles with its top players, so in past years McEnroe has built his roster around winning the doubles matches, relying heavily on Jack Sock, who is 7-2 in Laver Cup doubles.But without the big three playing for Team Europe, Patrick McEnroe, a vice captain and brother of John McEnroe, said, “we’re not as big an underdog in the singles as we were.”For instance, Denis Shapovalov has a career record of 10-8 against the six Team Europe players. So John McEnroe is aiming for more singles wins, choosing players like Reilly Opelka, who is approaching the Top 20, over Sock, who is an alternate for 2021.Opelka fits the model of McEnroe’s other captain’s picks, John Isner and Nick Kyrgios. “I’m bringing guys in to try and take the racket out of their opponent’s hands,” McEnroe said, referring to players with powerful serves.The week of practice leading up to the tournament serves several purposes for the teams’ leaders. “You need to figure out the doubles partners,” Enqvist said, “so you talk to the guys and try a couple of combinations. It’s important to have good chemistry.”When asked if he could have played doubles alongside Jimmy Connors had the Laver Cup existed in 1980, John McEnroe shrugged. “That would have been iffy,” he said. “I would like to think so, but one year we played Davis Cup together and didn’t talk the whole time.”Patrick McEnroe was amused by the notion. “It would definitely have been worth the price of admission,” he said, “but you’d have to be one strong captain to pull that off.”Reilly Opelka, an American player, in action at the United States Open this month. He will play for Team World at the Laver Cup.Geoff Burke/USA Today Sports, via ReutersThat chemistry goes beyond just doubles partners, Borg said.“We have at least two dinners together to build team spirit,” he said. As for potential conflicts arising from Alexander Zverev’s chastising of Stefanos Tsitsipas for bathroom breaks that he said were too long, Borg said he would be hands off and leave it to his players to work through it.Practical coaching is minimal, John McEnroe said: “The players’ coaches get very protective and call me all the time asking what I am going to do.”Still, he does try, because helping a player make even a slight improvement can make a difference. “I like to help players maximize their potential, and this is one way where they can get feedback from me,” he said. “And it’s not costing them anything.”Both captains submit lineup cards blindly (not knowing who the opponent will be) for the first day, then each gets a turn seeing the other’s lineup first for the next two days. Captains must also weigh the scoring rules: Matches are worth one point the first day, two on the next day and three on the final day.“You want to start strong on Friday, but you might want to save stronger players for Saturday because those are two-point matches,” Enqvist said.Unlike ATP Tour matches, the captains (and the team) are right there on the sideline. “I’m providing a combination of team building, tactics and psychological boosts,” John McEnroe said, though tactics take a back seat. “It’s hard to figure out something that drastic. It’s often basic reminders, but it’s not like I have to tell John Isner, ‘Serve big.’”Mostly it is an enhanced cheerleader’s role. “I give positive vibes,” Borg said.“These players are the best in the world and have played the other guys, so they know what to do and what not to do,” he said. “But if they’re not playing well, I can push them in a positive way.”With the big three replaced by newcomers like Caspar Ruud and Matteo Berrettini, Borg said, “I may be more hands-on and say a few more things this year.”McEnroe said his and Borg’s statures and personas did have an impact.“Even for Roger or Rafa, looking over and seeing Bjorn, they’ll say, ‘I want to make sure I do my thing,’ because Bjorn has an aura around him,” McEnroe said. “I hopefully bring an energy to our side.”Team Europe may be the favorite, but McEnroe has a solution: “I was suggesting that when I grew up, Russia wasn’t considered part of Europe, so we should get [Daniil] Medvedev and [Andrey] Rublev and that would level the playing field.” Medvedev won the United States Open on Sept. 12.In reality, Russia is in Europe and Asia, but the players hail from the European part.“John,” Borg said with a chuckle, “would want all the players.” More