TUCSON, Ariz. -- Jim Mora has spent the past three years rebuilding UCLA's depth, bringing in one strong recruiting class after another.
The ninth-ranked Bruins will have to rely on some of that depth Saturday against No. 16 Arizona and the rest of the season after losing three starters the first three weeks.
UCLA (3-0) lost tackle Eddie Vanderdoes to knee surgery in the season opener and cornerback Fabien Moreau suffered a broken foot against BYU last week.
More from FoxSports
The biggest blow was a season-ending knee injury to Myles Jack. A game-changing linebacker and a punishing running back in short-yardage situations, he was injured in a non-contact drill during Tuesday's practice.
"You'll have adversity," UCLA coach Jim Mora said. "It's how you handle it that defines you."
The Bruins may be hurting, but the Wildcats won't be taking them any less lightly.
Arizona (3-0) has yet to beat UCLA in three tries since Rich Rodriguez took over as coach, the only team he hasn't beaten in the Pac-12 South.
The Bruins embarrassed the Wildcats 66-10 in 2012 and had one of its worst offensive performances under Rodriguez in a 17-7 loss in Southern California last season.
The Wildcats have had some success beating top-10 teams in Tucson under Rodriguez, beating No. 9 Southern California in 2012 and No. 5 Oregon the next season.
"I don't think you have to tell them (the players) how big a game it is," Rodriguez said. "They know. They feel the buzz. They read. They watch TV. They can feel it. There won't be any problem getting their focus this week."
What else to look for in Saturday's game between UCLA and Arizona:
SCOOBY RETURN?: While UCLA lost its star linebacker, Arizona may get its best defensive player back. All-American Scooby Wright returned to practice this week after having surgery to repair torn meniscus in his left knee the first week of the season. Wright's availability is expected to be a game-time decision, but he could be a huge force for Arizona's defense if he returns.
ROSEN'S PROGRESS: UCLA quarterback Josh Rosen caught the nation's eye with an impressive performance in UCLA's opener. The freshman hasn't been quite as good the past two games, completing 33 of 65 passes for 329 yards, two touchdowns and four interceptions in wins over UNLV and BYU. The Bruins will need him to handle the pressure in what should be a wild Zona Zoo.
RUNNING WILDCATS: Because the Wildcats run a spread offense, they're often thought of as a pass-first team. But since Rodriguez became coach, Arizona has been one of the nation's best rushing teams, first with Ka'Deem Carey and now with Nick Wilson. Arizona leads the Pac-12 and is seventh nationally with 321 yards rushing per game and set a school record with 499 yards against Northern Arizona last week.
BRUINS RUN, TOO: With all the attention being paid to Rosen, it's been Paul Perkins who has carried the biggest load on offense. The junior is seventh nationally with 429 yards -- four behind Wilson -- and had a 219-yard game against BYU last week, most by a UCLA running back since 2006.
ARIZONA'S TEST: Arizona has one of the nation's weakest non-conference schedules and taken a bit of heat for it. The Wildcats were average in their opener against UTSA, but rolled over Nevada and crushed Northern Arizona 77-13. Arizona has been getting better with each game, but UCLA will be a huge step up in competition.