Teammates in Brooklyn, Rivals in M.L.S.

When Kevin Durant bought a stake in the Philadelphia Union last summer, he became the fourth member of the Nets with an ownership stake in Major League Soccer.

In the early days of Major League Soccer’s restart last summer, Jim Curtin, the coach of the Philadelphia Union, told his players that he had lined up a special guest for a video conference call. The Union players were in the league’s bubble at Walt Disney World, near Orlando, Fla., and because of health and safety protocols that limited large group gatherings, they had scattered to their hotel rooms for the call. A familiar figure soon appeared on their screens. Kevin Durant, one of the team’s new owners, had arrived to deliver a pep talk. As Durant’s speech — a message about what it takes to succeed and become a champion — morphed into a nothing-is-off-limits discussion, the players asked him about his N.B.A. title runs with Golden State, about his decision to join the Nets in free agency and about his then-ongoing rehabilitation from Achilles’ tendon surgery.