It isn’t even close. Isiah Thomas has been the Garden’s most successful basketball executive the past three years.

The Liberty begin their third straight trip to the WNBA playoffs Sunday riding a franchise-record-tying 10-game winning streak, brandishing a 22-12 record as they vie for the franchise’s first-ever title. They play host to the Mystics and superstar Elena Delle Donne at 5 p.m at Madison Square Garden in a one-game, winner-take-all contest.

Under Thomas’ guidance, the Liberty are 66-36 — the first time in franchise history the club posted three straight 20-plus seasons. Before Garden owner James Dolan made the shocking decision to bring on Thomas, a move met with a mound of controversy, the Liberty had missed the playoffs two straight seasons. With attendance flagging, Dolan considered selling his WNBA entity. Now Dolan has reason to be prouder of the Liberty than the woebegone Knicks.

“We started this year with championship expectations, and it has been encouraging to see how we came together towards the end of the regular season,’’ Thomas said in an email. “Our team emphasis over the past three seasons has been defense and rebounding. Our defensive execution played the biggest part in a record-setting third-straight 20-win season.’’

Indeed, during the 10-game romp, the Liberty allowed 68.1 points per game after giving up 80.1 points prior. It is the third straight year the Liberty led the WNBA in defensive field-goal percentage.

Nevertheless, the Liberty haven’t flourished in the postseason and dropped a one-and-done playoff home game to Phoenix last September.

“Ten in a row doesn’t really mean a whole lot except for playoff seeding,’’ Liberty coach and Thomas’ buddy Bill Laimbeer said. “In the one and done, you lose the next game and you’re out. Our players understand from last year the importance of one game.’’

The Liberty survived starting point guard Brittany Boyd’s season- ending Achilles tendon injury she suffered in the second game. The key to the turnaround from a 12-12 start was 3-point demon, Sugar Rodgers, an All-Star, agreeing to come off the bench as the “sixth man.” That allowed Laimbeer to start a more cohesive backcourt of Epiphanny Prince, a shooting guard who moved to point guard, and Bria Hartley.

In addition, superstar Tina Charles continued her domination up front. She averaged 19.7 points and 9.4 rebounds, finishing top-four in the league in both categories.

“Epiphanny and Sugar have shown what it means to be consummate teammates, embracing their shifting roles,’’ Thomas said.

Thomas has attended every home game. Dolan has made a bunch, too, savoring a basketball decision actually panning out.