Marcus LoVett hobbled onto the court with his foot in a boot, and though the game hadn’t even started, St. John’s already seemed to be behind.

The Red Storm was coming off a gutsy win over Tulane on the road, but St. John’s had lost its best scorer to an ankle injury. For a team this green, it should have been a devastating blow. Should have, because instead, St. John’s did a whole lot of growing up.

The result: an ugly but gratifying 76-70 non-conference win over Cal State Northridge at Carnesecca Arena on Monday night.

“Our flow wasn’t there and we kind of grinded out the game for the most part,” coach Chris Mullin said. “We’re in a position where any wins [are important] — seriously, that’s where we’re at . . . In any sport, in life in general, [when] you prove it to yourself, that’s when you take the next step . . . That’s where the real belief starts to happen.”

Freshman Shamorie Ponds scored a career-high 25 points and Bashir Ahmed had 13 points and eight rebounds for St. John’s, which beat back a breathless late-game attack by the Matadors.

The score was tied twice in the second half, and CSUN (3-6) took a one-point lead with 6:51 to go, but St. John’s scored the next seven to go up 68-62 with 4:08 left.

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Tavrion Dawson’s layup with 41 seconds left drew the Matadors within 72-70, but Ponds and Malik Ellison sank four free throws in the last 19 seconds to seal it.

The Red Storm shot 10-for-21 from three-point range, including four by Federico Mussini. St. John’s has 91 three-pointers in its first nine games, the most of any team in the Big East.

Unsurprisingly, the game plan and the rotation was altered significantly because of LoVett’s absence, and a lot of the touches fell to Ponds.

“I just tried to be more aggressive,” he said, “just be the leader out there and be more vocal.”

For now, Mullin said LoVett is day-to-day, but he had further tests done Monday night. The team is classifying it as a sprain, though that could change after X-rays.

“He’s a major key for us . . . [but] he just wants to see us win,” Ponds said. “This is our closest game and coming down to the wire . . . It wasn’t pretty, but we’ll still take it.”