How UCLA Can Win Pac-12 Without Superstar Myles Jack

The season-ending injury bug that has bitten so many great college football players through the first few weeks of the season just won't stop gnawing on the UCLA defense.

The biggest name for the Bruins is now out for the rest of the 2015 season, as versatile junior linebacker Myles Jack suffered a "significant knee injury" in Tuesday's practice, per Joey Kaufman of the Orange County Register:

Jack is the third veteran starter on UCLA's defense to go down with a serious injury within the first three games of the season.

Defensive tackle Eddie Vanderdoes tore his ACL in the season opener against Virginia, and cornerback Fabian Moreau was ruled out for the rest of the year earlier this week because of a broken bone in his foot.

Now the Bruins will have to manage without Jack as they enter this weekend's high-profile Pac-12 opener against Arizona, the team Jack rushed for 120 yards against in his breakout 2013 season.

Last year, as a sophomore, Jack had the second-most tackles for UCLA and was a second-team All-Pac-12 selection at linebacker.

Jack was off to an excellent start to 2015 on defense. He is currently third on the team in tackles and had a game-clinching interception of BYU quarterback Tanner Mangum late in UCLA's comeback victory last weekend.

The news of Jack's injury comes at a point in time when it looked like UCLA had the most momentum in the entire Pac-12.

On Sunday, the Bruins were ranked No. 9 in the AP poll. According to Jack Wang of Inside UCLA, this week marks the first time UCLA has been the highest-ranked Pac-12 team in 14 years.

In order for the Bruins to keep their dreams of clinching the highly competitive South Division and winning their first conference championship since 1998 alive, replacing Jack has to be an entire team effort.

Defensively, Jack may have been one of UCLA's best tacklers, but he isn't even one of the team's top two inside linebackers in that category for 2015. 

Name	Position	Total Tackles
Isaako Savaiinaea	LB	19
Jayon Brown	LB	16
Myles Jack	LB	15
Marcus Rios	DB	13
Kenny Clark	DL	12

The Bruins' top two defenders on the tackle charts, Isaako Savaiinaea and Jayon Brown, are both reserve players behind Jack and sophomore Kenny Young. 

Their early-season success and breakout performances against BYU are largely due to what could save UCLA's defense in the long run—a steady pattern of rotation at linebacker under new defensive coordinator Tom Bradley.

"Rotation is a big thing—keeping everybody on their toes and keeping everybody ready," Brown said, per Matthew Joye of the Daily Bruin. "[When] Isaak [went] in, he was ready and prepared for that because of the time he was getting in from the prior games."

Stephen Dunn/Getty Images

As Joye noted, Savaiinaea and Brown made big impacts in other areas besides racking up tackles. Savaiinaea emerged as a leader after Young was ejected in the first quarter, and Brown did well to spy Mangum and force Jack's late interception.

"Isaak's been ready to go," Jack told Joye after Saturday's game. "Isaak's played big games—he played against Stanford when [Eric Kendricks] got hurt [in 2013]."

That Jack quote is eye-opening to read several days later, as now Savaiinaea will be one of the players tasked with replacing Jack's incredible production on the defensive side of the ball.

As Jack tweeted Wednesday, it's now a "next-man-up philosophy" for the UCLA linebackers, and they're in good shape so far with Bradley's system of rotation.

In addition to the reserve linebackers, the rest of UCLA's defense needs to step up its production, especially in pass coverage.

Jack had more responsibility against the pass so far in 2015, and he received rave reviews for his play there against BYU.

"Basically every time [Jack] was lined up in man coverage he locked up his guy," David Woods of Bruin Report Online wrote. "His interception at the end was a pure instinctual play. He also played with good discipline throughout, which was great to see."

Now without Jack, UCLA will face several high-powered passing attacks in its race for the Pac-12 title.

Arizona State's Mike Bercovici (488 yards) and Cal's Jared Goff (303 yards) had big performances in losses last season, and the Bruins will line up against quarterbacks such as Arizona's Anu Solomon and USC's Cody Kessler. 

Stephen Dunn/Getty Images

While Jack no longer has as big of an impact on the UCLA offense as he did as a freshman "runningbacker"—although he has one rushing touchdown to his name this year—his injury will force the Bruins to get better on that side of the ball, too.

Anytime a team loses a defensive leader, the whole team feels the impact. With three key defensive stars now out for the season, the pressure is on the UCLA offense to improve.

Quarterback Josh Rosen was phenomenal in his first game for the Bruins, but he came back down to earth last Saturday in a three-interception performance against BYU. 

With the defense taking serious hits in the injury department, Rosen needs to take care of the ball better as UCLA heads into the Pac-12 schedule. The last thing UCLA will want to do is give opponents shorter fields against a banged-up unit.

"When you throw three interceptions and you feel like there are 67,500 people on your case, and you feel like you've let your team down, you have to find a way to dig yourself out of that," UCLA head coach Jim Mora said, per Ryan Kartje of the Orange County Register. "...We're going to look back and this will be a great game to learn from."

Jae C. Hong/Associated Press

UCLA has showcased some strong defensive depth behind Jack and the other injured starters this season, and the offense is starting to find a great groove on the ground behind Paul Perkins and Nate Starks. 

If they can improve in a few more areas, such as ball security and pass coverage, these Bruins are still in great shape to make a run in the Pac-12 South.

Losing an incredible player like Jack is undoubtedly a big blow, but UCLA looks prepared to handle it on paper. Now it's time to deliver on the field in one of the nation's toughest leagues.

Recruiting information courtesy of 247Sports. Unless otherwise noted, statistics courtesy of cfbstats.com. 

Justin Ferguson is a college football writer at Bleacher Report. You can follow him on Twitter @JFergusonBR.