The positive momentum toward a healthy Ben Simmons carrying the Nets back to relevance lasted one game.

Simmons was set to miss Wednesday’s matchup with the Suns at Barclays Center with a left knee contusion, a step back after a long-awaited step forward.

Simmons — who had sat for nearly three months with a nerve impingement in his lower back — looked like his old self in an impressive 18 minutes during Monday’s win over the Jazz.

But in the closing minutes, he went up to block a layup from Talen Horton-Tucker, who did not rise much for the shot.

Simmons’ right leg landed atop Horton-Tucker, while his left leg landed hard and awkwardly on the floor.

Simmons remained on the floor for a few moments before rising and subsequently was subbed out of a game in which the Nets were cruising.

Simmons has a history of left knee issues and received platelet-rich plasma injections last season when the knee bothered him.

His agent, Bernard Lee, suggested that the player and team are simply being cautious.

“This is being done as he has a small irritated spot,” Lee wrote on Twitter, “the thought is by being cautious here with 3 days until the next game this can be put to rest and he can continue to work his way back to 10/10 game shape.”

After missing 38 straight games from early November to late January, Simmons missed one more.

In his one-game return, Simmons demonstrated how much the team needs him.

The Nets played like they rarely had this season, pushing the pace and moving the ball while destroying Utah.

Playing just in spurts off the bench, Simmons flirted with a triple-double (10 points on 5-of-5 shooting with 11 assists and eight rebounds).

But the reality that his return lasted one game before another setback underscores the durability questions that will surround Simmons until he can regularly appear on the court.