SOUTH BEND, Ind. (AP) — Notre Dame heads into an off week feeling good about its 37-34 victory over Arizona State, particularly the play of its defense, yet knowing it will be without middle linebacker Jarrett Grace for the rest of the season because of a broken right leg.

Grace, who is tied for the most tackles on the team with 40, underwent surgery Sunday in Dallas to have a rod placed to help heal the fibula fracture. He is expected to spend several more days in the hospital and it could take him four to six months to recover.

"Obviously a big loss for us," coach Brian Kelly said Sunday.

Dan Fox, who was the starter at the beginning of the season and has played at both the inside linebacker spots, will replace Grace as the starter while the Irish will use the free week to determine who will be his backup. Fox had two big plays in the victory against the Sun Devils in Arlington, Texas, recovering a fumble to set up a touchdown in the third quarter and intercepting a pass by Taylor Kelly and returning it 14 yards for a touchdown with 68 seconds left in the game that clinched the victory.

It was the best performance so far this season for the Irish, which consistently put pressure on Kelly, sacking him six times and, forcing three turnovers and holding a Sun Devils squad that scored 62 points a week earlier against a good USC defense to three touchdowns and two field goals. The other Arizona State touchdown came on a 37-yard interception return by Osahon Irabor.

"I thought their defense played at a really high level. I thought that was the difference in the game," Arizona State coach Todd Graham said.

Although it wasn't the dominating defense the Fighting Irish used to get to the BCS title game last season, it was the closest Notre Dame (4-2) has come so far this season. Notre Dame held the Sun Devils (3-2) to 65 yards rushing. The Irish came into the game with three sacks. Notre Dame linebacker Prince Shembo, who had his first three sacks of the season after having 7.5 last season, said the Irish having a nine-minute advantage in time of possession was key.

"We were fresh when we got on the field. We had a lot of fresh legs coming in," Shembo said.

Midway through the season, the Irish are ranked 50th in the nation in total defense, giving up 374.5 yards a game after ranking seventh in the nation last year at 305.5 yards a game. They are ranked 58th in scoring defense, surrendering 25.5 points a game after ranking second in the game last season at 12.8 points.

"We know we're developing our own identity. There are a lot of guys that left so I think we've just done a great job at coming together," linebacker Jaylon Smith said.

There were some things for the Irish to be concerned about, though. In the fourth quarter, on a third-and-20, Kelly completed a 31-yard pass to Kevin Ozier to help set up a tying touchdown for the Sun Devils. The Irish, who only allowed one touchdown drive of 75 yards or longer during the regular season last year, let the Sun Devils drive 75 yards on seven plays in 57 seconds to close to 37-34 with 11 seconds left.

"There are things that we have to continue to improve on. Nobody was happy with the last drive," Kelly said.

But midway through the season, Kelly is pleased with the way the defense is coming together heading its annual rivalry game with USC on Oct. 19.

"I'm not saying that, you know, we've got a spectacular defense, but we have a solid defense that is getting better week in and week out," he said.

Kelly said he will give starters who have played extensively a chance to rest this week, while younger starters will get extra work. He specifically pointed out center Nick Martin, who has been called for several snap infractions the past two games, and receiver DaVaris Daniels, who appeared to run several routes wrong against Arizona State, as players who will be getting extra work this week.

"We'll work those guys that need to continue to get some more work, and we'll look at those guys that need some time off to really get healthy," Kelly said.

Kelly also announced that senior receiver Daniel Smith, primarily used as a blocker, has a broken left ankle and will undergo surgery when the swelling subsides. He also is out the rest of the season.