LeBron James? Tom Brady? Sidney Crosby? No. The most powerful force in sports is Cap Space | Mike Sielski

The most unstoppable force in sports these days isn’t LeBron James or Tom Brady or Sidney Crosby. It isn’t Steph Curry open from three or Saquon Barkley in the open field or Alex Ovechkin open in the left circle. It isn’t the New England Patriots or the Golden State Warriors or a goaltender who happens to get hot once the playoffs begin.

It’s Cap Space. The NBA trade deadline just passed, and the NHL’s is coming up, and the NFL’s free-agency period begins next month. So Cap Space is never more important than it is right now.

Cap Space attracts great players. Cap Space changes teams’ fortunes. Cap Space wipes away the bad and creates the opportunity for good. Cap Space is versatile. Cap Space fills any role on any team. Cap Space wins championships. Cap Space is a surefire first-ballot Hall of Famer. Cap Space gets it done.

Cap Space, more and more, defines whether a particular franchise in a particular league — be it the NFL, the NBA, or the NHL — is trending in the right direction. It sets the parameters of the debate.

Does that team have enough Cap Space? What will its general manager do to create some Cap Space, and what will the GM do once he has Cap Space? Will he rely on Cap Space to sign a free agent or two? Will he make a big trade to fill some of that Cap Space? Will he roll over some Cap Space into next season so he might make even bigger and better acquisitions and changes?

Cap Space has power. (So does Cap Space’s baseball-oriented cousin, Payroll Flexibility, though not quite as much.)

People might think, for instance, that the Eagles became an elite team once they drafted Carson Wentz. That’s not quite right. Wentz was good right away and has been genuinely great for long stretches of his brief career, but there was another factor that was just as vital to the Eagles’ rise.

Because Wentz has been on his inexpensive rookie contract for the last three seasons, the Eagles could free up Cap Space by making Wentz their starter. Cap Space led to the other signings and trades that Howie Roseman made to turn the Eagles into NFL champions. Roseman doesn’t sign Alshon Jeffery or Chris Long — or, most notably, Nick Foles — without Cap Space. The Eagles won a Super Bowl without Wentz, but they were never going to win one without Cap Space.

Similarly, Cap Space and Brady have a symbiotic relationship. By accepting a below-market salary from the Patriots, Brady allows them to maintain Cap Space, which in turn allows Bill Belichick to build and rebuild the roster annually, which allows the Patriots to keep winning Super Bowls.

Without Cap Space, Tom Brady would just be the famous husband of a more-famous supermodel. He would be unfulfilled. He would be just another guy selling a specious diet plan. He would be sad. But Brady keeps Cap Space around, because Cap Space keeps making Brady happy.

Cap Space makes everyone happy, actually. Why did Kevin Durant sign with the Warriors? Cap Space. Why did the Knicks recently trade their best player, Kristaps Porzingis, and why do they hope they can sign two max-contract free agents this offseason — maybe even Durant — and turn themselves around? Cap Space. What has kept the Flyers mired in mediocrity for the last several years? Easy. They haven’t had enough Cap Space.

What was Sam Hinkie’s first goal when he initiated The Process with the 76ers? Duh. Creating Cap Space. And why do the Sixers believe that they can sign Ben Simmons, Tobias Harris, and Jimmy Butler to max contracts and keep chasing championships after this season? Because after trading Markelle Fultz, they have the necessary Cap Space.

Used wisely, Cap Space helps an NBA team balance its lineup. A team can get stars and role players, shooters and defenders, veterans and up-and-comers. It can add pieces during a season. On the court, Cap Space creates floor space.

Sure, teams can win without Cap Space. But usually only after they’ve had Cap Space, after Cap Space had been there and had established the conditions under which the team could thrive. Like any good leader in any sport, Cap Space leaves a legacy.

No player or coach or big-brained executive can compare to Cap Space. In fact, no other Cap can compare to Cap Space. Cap Space is more influential than former Islanders head coach Jack Capuano, who in his six-plus seasons with the Islanders won one playoff series. Or defenseman Kyle Capobianco, who has appeared in all of three NHL games, with the Arizona Coyotes. Or goaltender Frank Caprice, who, having won just 31 of the 102 games he played for the Vancouver Canucks from 1982 through 1988, likely would have been a Cap Casualty, had there been such things back then.

And here’s the best part about Cap Space: Cap Space never fails. Think about it. Even when a team has Cap Space and doesn’t succeed, it isn’t Cap Space’s fault. It’s never Cap Space’s fault. The team might sign the wrong players to the wrong kinds of contracts and misuse Cap Space, but you can’t blame Cap Space for that.

Getting Cap Space is hard, but keeping it is harder, and once you have Cap Space, you have to hold on to it. Otherwise, you’ll fall into the most hopeless and destructive situation in sports.

Seriously, do you want The Window to Close on your team?