Running by Reynosa Spurs Sylmar, 34-7 : High school football: He comes off bench after Crenshaw’s injury to awaken Spartans, who advance to City Section 4-A semifinals against Carson.

Sylmar Coach Jeff Engilman has one thing to be thankful for this holiday: If one running back goes down for his team, there is more than one capable replacement waiting on the sideline for his name to be called.

Such was the case Wednesday night when Tyrone Crenshaw, the defending City Section 4-A Division player of the year, left the game briefly in the second half to tend to his chronic injured ankle.

Seconds after Crenshaw hobbled off the field, his replacement, Mark Reynosa, busted loose for a 77-yard touchdown to fuel a 34-7 victory over Venice in a 4-A quarterfinal-round game.

Sylmar (10-1-1) held a precarious 14-7 lead late in the third quarter and its offense had been sputtering since the first period.

But on the threatening, albeit motivational, advice of Engilman, who told him, “Don’t fumble the football,” Reynosa hit a hole on the right side and exploded down the field.

“That was important,” Engilman said. “I think that was the turning point because we were losing momentum quickly.”

And what were Engilman’s words to Reynosa after the big score?

“He said, ‘Tuck your shirt in. You look sloppy,’ ” Reynosa said.

Engilman’s response to Reynosa epitomized his mood from the second quarter on. “Our offense didn’t play well, our defense didn’t play well . . . not sharp at all.”

Nonetheless, the victory sets up a rematch of last year’s championship game with Carson, which beat Garfield, 61-14. Sylmar shut out Carson, 17-0, in the final.

Despite Engilman’s disgust with the Spartans’ play, Crenshaw looked good. Crenshaw, who returned to the game with fresh tape on his right ankle after Reynosa’s run, rushed for 173 yards in 24 carries and scored on a 31-yard run.

Reynosa finished with 101 yards in six carries and scored his second touchdown on a two-yard run with 1:05 remaining.

Sylmar started strong despite a second-quarter lapse.

Myron Brown recovered a Venice fumble on the opening kickoff and Sylmar’s offense set up shop at the Gondoliers’ 47. After a couple of miscues by quarterback Eddie Lopez, Crenshaw took over.

First carry, 11 yards. Second carry, he turned the corner around the left side and raced 31 yards to give Sylmar a 7-0 lead less than two minutes into the game.

Sylmar’s defense forced a punt by Venice (9-3) after three Robert Hayes runs failed to gain a first down.

Sylmar went 62 yards in eight plays and scored again on an 11-yard end-around by Dwight Patton to give the Spartans a 14-point lead. But, then the offense stalled.

Venice used up nearly eight minutes after forcing Sylmar’s first of four punts. The Gondoliers went 80 yards in 15 plays and scored on Michael Blasi’s eight-yard pass to Aaron Burnes for their only score.