Provo • When spring football practices begin for BYU next Monday, the focus will likely be on the offense, just like last year, when Jeff Grimes replaced Ty Detmer as the Cougars’ offensive coordinator and went about rebuilding a unit that was awful the previous season.

Those are the questions that will dominate camp, which runs through March 28.

Meanwhile, BYU defensive coordinator Ilaisa Tuiaki and his staff — linebackers coach Ed Lamb, safeties coach Preston Hadley and cornerbacks coach Jernaro Gilford — will go about their business quietly trying to get more out of a defense that also improved in 2018.

Under head coach Kalani Sitake, Tuiaki’s defense was serviceable in 2017, when the Cougars were borderline inept on the offensive side of the ball. The defense was clearly the strength of the team in 2018 as the Cougars rebounded with a 7-6 record and routed Western Michigan in the Famous Idaho Potato Bowl.

What’s next?

“We felt like [the defense] had a good year," Tuiaki said, “but there’s always room for improvement.”

That’s called being modest. The Cougars improved markedly in the four major defensive statistical categories. They finished No. 18 in the country in total defense, allowing 324.1 yards per game. They were No. 24 in scoring defense (21.4 points per game), No. 27 in rushing defense (130.1 yards per game) and No. 29 in passing defense (194 yards per game).

So what will the defense look like in 2019?

Tuiaki acknowledged at BYU’s Signing Day news conference Feb. 6 that replacing three stars — defensive end Corbin Kaufusi, defensive back Michael Shelton and linebacker Sione Takitaki — will be difficult. Takitaki will participate in the NFL Scouting Combine later this week in Indianapolis.

Lamb faces the biggest rebuilding job among the defensive coaches, because four other linebackers also exhausted their eligibility: Butch Pau’u, Rhett Sandlin, Tanner Jacobson and Riggs Powell.

Flash linebacker Zayne Anderson played in four games last year before having season-ending shoulder surgery and will return to anchor the linebacking corps.

Also back is Isaiah Kaufusi, who emerged the latter half of the season before suffering a season-ending injury against Utah that kept him out of the bowl game. Former four-star recruit Chaz Ah You is back from a church mission and will play linebacker after starting his BYU career as a safety.

Another safety, Sawyer Powell, successfully petitioned the NCAA to get a season back and will return in 2019 for his final year of eligibility.

On the defensive line, younger brother Devin Kaufusi is expected to step in for Corbin Kaufusi, who likely didn’t get invited to the combine because he needed multiple surgeries when the regular season ended. Senior Trajan Pili and junior Khyiris Tonga will return after starting most of the games last year.

Juniors Zac Dawe, Bracken El-Bakri and Uriah Leiataua and sophomores Lorenzo Fauatea, Alden Tofa and Earl Tuioti-Mariner should also add depth.

Shelton, who was also a dangerous punt returner, is the only key defensive back moving on, but Gilford has learned that BYU never can have too many capable and experienced DBs. That’s why the coaching staff searched the junior college ranks for safeties and cornerbacks in the offseason and found a pair of teammates from Mount San Jacinto College in Southern California who they believe can make immediate impacts.

The Cougars signed 5-11, 170-pound Eric Ellison in December and 6-foot, 190-pound cornerback Dimitri Gallow in February.

“Dimitri is more game-ready right now,” Gilford said. “Eric has a very, very high ceiling. He played running back, receiver, defensive back and kick returner at the JC level. You don’t find that too often, a JC guy playing both ways.”

Lamb said Gallow, who was injured in 2018 and missed the season to concentrate on academics, is one of the best JC or high school players he has ever seen play bump-and-run coverage.

“He stands at the line of scrimmage, does not back up, stays low, gets in front of the receiver,” Lamb said. “Watching his film, you can see how the opposing quarterback cannot look in that direction, because the receiver is not off the line of scrimmage. So Dimitri will bring that physicality to us and teach some of the other guys how to play with his success.”

The defense will also be bolstered in 2019 by several returned missionaries, including defensive linemen Freddy Livai, Tyler Batty and Seleti Fevaleaki, linebackers Ben Bywater, Solofa Funa, Preston Lewis and Keenan Pili and defensive back Ammon Hannemann.

Alex Miskela, a linebacker from Los Alamitos High in Southern California who signed in February 2018 but did not join the team in the fall, is now enrolled and will participate in spring camp.

How BYU’s defense improved in key statistical categories from 2017 to 2018

Scoring defense: From No. 46 (24.7 points per game) to No. 24 (21.4 ppg.)

Total defense: From No. 51 (372.8 yards per game) to No. 18 (324.1 ypg.)

Rushing defense: From No. 44 (147.6 ypg.) to No. 27 (130.1 ypg.)

Passing defense: From No. 67 (225.2 ypg.) to No. 29 (194 ypg.)

BYU’s key defensive losses: DE Corbin Kaufusi, DL Merrill Taliauli, LB Sione Takitaki, LB Butch Pau’u, LB Rhett Sandlin, LB Tanner Jacobson, LB Riggs Powell, DB Michael Shelton.

BYU’s possible defensive additions: DB Dimitri Gallow (Mount San Jacinto College), DB Eric Ellison (Mount San Jacinto College), LB George Udo (Berean Christian High School), LB Chaz Ah You (mission), DL Freddy Livai (mission), DB Ammon Hannemann (mission), DL Tyler Batty (mission), DL Seleti Fevaleaki (mission), LB Ben Bywater (mission), LB Solofa Funa (mission), LB Preston Lewis (mission), LB Keenan Pili (mission), LB Alex Miskela (Los Alamitos High School).