The Alabama Crimson Tide are the defending national champions and will have sky-high expectations heading into the 2018 season.

However, that doesn’t mean everything will be easy in Tuscaloosa, as the Tide have a few questions that need to be answered before Week 1, including at the starting quarterback position.

And the quarterback battle isn’t even the biggest concern for coach Nick Saban. During an appearance on SportsCenter on Tuesday, Saban said that he’s most worried about the fact that the Tide only return three starters on defense (via 247Sports):

“That’s probably the No. 1, and nobody talks about it,” he said. “Everybody wants to talk about the quarterback situation, but no one talks about what we have to do to rebuild the defense. And I think that’s the No. 1 concern. … I think it’s a concern in terms of how that part of our team develops.”

The defensive rebuild includes replacing all the starters in the secondary. In fact, the only starters returning to the squad are DL Isaiah Buggs and Raekwon Davis and LB Anfernee Jennings.

Yes, the Tide have plenty of young talent ready to step into the open roles, but that doesn’t mean the transition will be smooth this summer.