Reeves Nelson, Joshua Smith might not face Arizona

UCLA could be forced to take on the most dynamic big man in the Pacific 10 Conference without its top two frontcourt players.

Sophomore forward Reeves Nelson and freshman center Joshua Smith returned to practice on a limited basis Tuesday, but their availability for the Bruins’ game against Arizona on Thursday in Tucson will be a game-time decision.

Smith has been sidelined with a head injury since early in UCLA’s victory over California last week, and Nelson sprained his left ankle with about eight minutes left in a triumph over Stanford two days later. Smith participated in some contact drills during practice Tuesday, but Nelson, who has been wearing a walking boot, did not.

Both players sat out practice Monday, though Coach Ben Howland said Tuesday that Smith had passed every medical test given to him.

The absence of either player would be an especially big blow considering the Bruins will face Arizona forward Derrick Williams, who is averaging 19.7 points and 8.1 rebounds. Nelson is UCLA’s leading scorer and rebounder, averaging 13.9 points and 8.0 rebounds, and Smith averages 9.8 points and 6.8 rebounds.

If Nelson or Smith is unavailable, UCLA will turn to freshman center Anthony Stover and sophomore forward Brendan Lane. Howland said Stover would defend Williams to start the game regardless of whether Smith plays in an effort to help keep Smith out of foul trouble. But the coach expected every available big man to guard Williams at some point.

“It’s going to be multiple guys,” Howland said.

New middle man

In the grand scheme of UCLA’s season, Stover was a small fry most widely known for being sickened by some bad chicken chili cheese fries.

Then came last week, when the redshirt freshman and his 7-foot-6 wingspan took center stage in the starting lineup against California and Stanford.

Stover played 38 minutes in the two games, more than he had played in the previous 10 games combined. He set career highs with five points and five rebounds in 23 minutes during UCLA’s 68-57 victory over Stanford.

The 6-foot-10 center is expected to be in the starting lineup again when the Bruins play Arizona, with the winner taking over sole possession of second place in the Pac-10.

“Now that I’m starting,” Stover said, “I’m still doing the same things, trying to get out there, rebound and play as well on defense as I can.”

Stover’s promotion from benchwarmer to starter had more to do with Howland’s desire to keep Smith out of foul trouble than any breakthrough by Stover. Howland said Stover was starting instead of Lane because Stover “gives us a better post presence early in the game defensively.”

Stover, averaging 0.6 points and 1.3 rebounds in 6.8 minutes, is thrilled merely to be playing after sitting out last season as a redshirt, a decision he acknowledged initially upset him.

“But after the fact I was OK with it,” Stover said. “I knew why [Howland] wanted to redshirt me, to prepare me for times like these, so I’m happy that I did redshirt.”

ben.bolch@latimes.com