SOUTH BEND, Ind. (AP) — The Notre Dame offense the past four years hasn’t much resembled the squads Brian Kelly coached at Cincinnati and Central Michigan.

Not even close.

The Irish are on pace to be the worst offense Kelly has had in 10 years of coaching at the FBS-level and may have hit rock bottom in the second half Saturday against USC with the Irish unable to do anything behind backup quarterback Andrew Hendrix after starter Tommy Rees went down with a neck injury.

Even with Rees expected to play Saturday at Air Force (1-6), there are concerns about the Irish offense, which is ranked 85th in the nation in total offense at 374.3 yards a game.

That’s the worst output for the Irish in four seasons under Kelly, and markedly worse than last season when the Irish averaged 412 yards a game, which was still only 54th in nation.

Kelly talked last spring about he hoped Notre Dame would be able to sometimes switch to the kind of no-huddle, hurry-up spread attack that Cincinnati used under him to finish fourth in the nation in scoring in 2009 at 38.6 points a game.

He talked in August about the offense needing to carry more of the burden this season after the Irish rode a dominant defense to the BCS title game. So far, though, the Irish offense hasn’t been holding up its end.

Kelly wouldn’t say Tuesday, why he hasn’t been able to have the success at Notre Dame offensively as he has elsewhere, other than again saying defense is the key to winning at Notre Dame.

“I’m not going to answer the question. Look at college football, look around college football, the teams that are scoring a gazillion points, it’s not innovative gurus on offense,” he said.

Asked again why he hasn’t been able to do at Notre Dame what he’s done at other stops, Kelly replied: : “Consistency. You have to be consistent on offense.”

The Irish were dealt a blow this season when last year’s starter, Everett Golson, was suspended from school for the fall semester for poor academic judgment. That came after Gunner Kiel, a top-rated quarterback coming out of high school, announced he was transferring.

Kelly named Tommy Rees, who started 18 games the previous three seasons, as the starter. The problem with Rees is he isn’t the running threat Golson is, and opposing defenses have crowded the line daring Rees to beat them with his arm.

The Irish are passing the ball slightly better than last season at 238 yards a game, 16 yards more than in 2012, but they are rushing the ball for 54 yards less a game.

Rees is completing 53 percent of his passes this year, down from 65 percent through seven games two years ago, the last time he was the starter. Kelly said it’s because defenses are making it more difficult by playing man-to-man coverage.

“Penalties are not as severe, hugging and holding. So you’re seeing a lot more man coverage, consequently your percentages are going down,” he said.

Some fans began questioning whether the Irish should switch quarterbacks after Rees struggled against Oklahoma, completing just 9-of-24 passes for 104 yards with three interceptions. After seeing Hendrix go 0-for-4 against USC, managing just 27 yards of total offense on 23 plays, Irish fans were relieved Tuesday when Kelly said Rees is expected to start Saturday.

Kelly said he still has confidence in Hendrix.

He has confidence as well in Rees, who started 12 games as a sophomore, is completing 53 percent of his passes this year, down from 65 percent through seven games two years ago. Kelly said it’s because defenses are making it more difficult by playing man-to-man coverage.

“Penalties are not as severe, hugging and holding. So you’re seeing a lot more man coverage, consequently your percentages are going down,” he said.

Kelly said the Irish will give Hendrix and freshman Malik Zaire more time in practice this week just in case. Kelly, who used five quarterbacks at Cincinnati in 2008 because of injuries in leading the Bearcats to the Orange Bowl, was asked what went through his mind when he saw that Rees was injured, knowing he had limited options.

“This has not been the easiest run in four years here at Notre Dame with quarterbacks. So we’re prepared for it at this point,” he said.

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