Aldon's Smith's defensive skill set will be tough to replace, says Niners DC

SANTA CLARA, Calif. -- One of the most appealing aspects of Eric Mangini taking over as the San Francisco 49ers' defensive coordinator was the thought of having a happy and healthy Aldon Smith at his disposal for a full 16-game schedule.

That, obviously, is no longer a possibility with Smith cut on Friday in the wake of his being arrested Thursday night, his fifth arrest since the Niners made him the No. 7 overall draft pick in 2011, his third arrest involving DUI.

So how big of a loss is it, then, for Mangini, and how big of an opportunity is it for other players?

"A guy like Aldon is not a guy that you just can replace," Mangini said following Sunday's practice. "He's got a unique skill set. But one of the things that we focused on defensively is building flexibility, in terms of what we can play, and then building flexibility with who's going to play there."

Thus far, Corey Lemonier has seen the most first-team reps at Smith's old right outside linebacker spot, while rookie Eli Harold saw the most overall reps there. Plus, Ahmad Brooks has shifted over from the left side, with Lemonier going to the left.

There is also Aaron Lynch, who has been slowed all offseason by a hamstring injury.

"We've been moving those parts around to play left and right so we wouldn't have to play guys in the same spot the whole time," Mangini said. "I think the defense has some flexibility built into it as well.

"You can't easily replace someone of that caliber, but we'll find ways collectively to get that done and there's great opportunities -- great opportunities -- for guys that may have had more limited roles had [Smith] been here."