The offseason was not a kind one to the Arizona defense. Three starters went down with a torn ACL — Jonathan McKnight, Jake Fischer and Adam Hall — and backup tackle Willie Mobley also tore an ACL playing pickup basketball.

Here’s a look at each of the Wildcats that went down with ACL injuries during the offseason:

#33 Jake Fischer

5-foot-11, 225 pounds

Junior linebacker

After starting eight games as a sophomore in 2010, Fischer was poised for a breakout year in 2011 before going down in Arizona’s spring game. He racked up 58 tackles last season and notched two interceptions and two pass break-ups. Fischer’s absence may be magnified by his replacement — neither junior college transfer David Lopez or freshman Rob Hankins has taken a Division I snap. But Arizona may be able to mask Fischer’s loss a little bit by playing more nickel defense, which replaces a linebacker with a defensive back.

#12 Adam Hall

6-foot-4, 220 pounds

Junior safety

Hall may have been the biggest playmaker in Arizona’s secondary. After starting seven games in 2010, he was tied for the team lead with two interceptions and had the ability to change the game with violent hits. Hall’s size also made him a force in the secondary. Furthermore, Hall showed up when the stage was the biggest; he recorded a career-high of 11 hits at Oregon and also had a 22-yard interception return against the Ducks.

#6 Jonathan McKnight

5-foot-11, 175 pounds

Sophomore cornerback

Coaches said McKnight had been Arizona’s most impressive defensive player in fall camp up until he went down with a torn ACL just more than a week before the season opener. A true sophomore, McKnight was slotted to start opposite either senior Trevin Wade or sophomore Shaquille Richardson, and he was likely to see time in punt return duties. McKnight appeared in all 13 games as a freshman, breaking up two passes and picking up 12 solo tackles.
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#34 Greg Nwoko*

6-foot-2, 235 pounds

Junior running back

If Nwoko had entered the 2011 season in good health, Arizona would likely be using more of a platoon at running back. Instead, senior Keola Antolin will likely get the majority of the carries, with Daniel Jenkins and Ka’Deem Carey splitting however many are leftover. Nwoko’s numbers don’t jump off the page — he was Arizona’s third-leading rusher in 2010 with 277 yards — but he’s a physical runner, a complement to the little guys in Antolin and Jenkins. Nwoko averaged 4.7 yards per carry in 2010.

#96 Willie Mobley

6-foot-2, 280 pounds

Junior defensive tackle

Though he likely wouldn’t have started, Mobley would have seen significant time in the rotation at defensive tackle if he hadn’t torn his ACL playing basketball during spring practice. Mobley appeared in 10 games in 2010 as a redshirt sophomore, picking up seven tackles and a half-sack. 2010 was Mobley’s first year playing football since redshirting at Ohio State in 2008. Mobley attended Orange Coast Community College in Costa Mesa, Calif., in 2009, but didn’t play.