Welsh and Ali sit out in Bruins’ 89-80 victory over Louisiana Lafayette

With six seconds left in the game Tuesday night, after UCLA was all but assured a victory over Louisiana Lafayette, Coach Steve Alford still crouched by the scorer’s table with his hand over his forehead.

The Bruins’ 89-80 victory over the Ragin’ Cajuns at Pauley Pavilion was their fifth in a row. But UCLA frustrated its coach and fans for much of the game.

The 22nd-ranked Bruins held a 19-point lead in the first half. Midway through the second half, the lead was down to four, and Alford’s aggravated shouts cut across a sparse winter-break crowd.

“We definitely took our foot off the gas,” forward Tony Parker said. “It became a real dogfight toward the end, but if we would’ve kept our foot on the gas, we would’ve made it way easier on ourselves.”

UCLA (8-3) was two days removed from an emotional victory on the road against Gonzaga.

Prince Ali, who left that game with a bone bruise to his left knee, was unable to play Tuesday (Alford called his status day-to-day). On Tuesday morning, Thomas Welsh was also ruled out with a stomach virus.

A letdown would not have been a surprise.

There was no letdown early. The Bruins scored the game’s first eight points. UCLA had held talented Ragin’ Cajuns forward Shawn Long in check. With seven minutes remaining in the first half, UCLA led by 19.

“We haven’t been up 20 in a while,” Steve Alford said. “And then all of a sudden, we’re throwing behind-the-back passes, we’re throwing no-look passes, we shut down our defense.”

At one point, Isaac Hamilton did all three. Late in the first half, he plunged into the lane, then flipped a one-handed, no-look pass behind his back to no one in particular. Louisiana Lafayette (3-5) scored on the next possession to make it a single-digit game.

Soon, Long found a rhythm. He finished with 26 points and 16 rebounds. And UCLA’s perimeter defense again became porous. The Ragin’ Cajuns made 13 three-pointers.

The defensive lethargy, Steve Alford said, was part of a troublesome pattern. In some games, he said, the defense played with constant intensity.

“I really saw it against Gonzaga, and I saw it against Kentucky,” he said. “And Long Beach. When we had to. And Louisiana Lafayette. When we had to. And that’s the danger.”

Offensively, UCLA did just enough. At the end of the first half, Bryce Alford made two three-pointers to halt a Ragin’ Cajuns rally. He ended with 27 points, a season high, and seven assists. Parker scored 19 points with nine rebounds.

In the second half, after Louisiana Lafayette had pulled within striking distance with two minutes left, Alford made another three-pointer to effectively seal the game.

This season, Steve Alford said, Bryce Alford is “really understanding the time we need for him to make a big shot.”

The only worry, Steve Alford said, was that Bryce had to log 38 minutes in the middle of a grueling stretch of games.

As a coach, Steve Alford said he would monitor his son’s minutes in practice this week. As a father, he has less sympathy.

“I’ve told him several times, his daddy played 38 minutes a game back in the era of tight shorts,” Steve Alford said.

“So it can be done.”

zach.helfand@latimes.com