SANTA CLARA, Calif. -- Vic Fangio had high praise for two of his key San Francisco 49ers defensive players, both of whom have dealt with major adversity.

The 49ers' defensive coordinator has been impressed with what he has seen from cornerback Chris Culliver and linebackers Aldon Smith in the early going of training camp. Culliver missed all of last season with a torn ACL, and Smith is trying to put a myriad of off-field issues behind him.

Fangio said Culliver, who suffered the injury in last season's training camp, looked completely recovered from his injury in Thursday's first training camp practice.

"I was really pleased with the way he looked physically," Fangio said of Culliver. "Kudos to our medical staff and everyone that's worked with him. Kudos to him for the work he's put into his rehab. He looked fine to me yesterday. I didn't see any indication that this was a guy that just came off a year-long rehab."

Fangio was also effusive about Smith's approach to the game.

"I think everything's good for him right now," Fangio said. "I think he's in a really great spot. Both physically, like he said, and I think he's in a great spot mentally, emotionally."

Smith could face suspension from the NFL because of his off-field issues. The 49ers are already likely to play without star inside linebacker NaVorro Bowman for about half the season, as he recovers from a torn ACL he suffered in January.

Fangio said it will be "challenging" if the 49ers have to play a stretch without both key linebackers. But he noted the 49ers were 5-0 when Smith missed five games when he was in a substance abuse treatment center and star linebackers Patrick Willis missed two games due to an injury.

"We will find a way," Fangio said.

Fangio is completely flexible when it comes to who replaces Bowman during the first half of the season. Michael Wilhoite, who played for Willis last year, and rookies Chris Borland and Shayne Skov are all vying for the job. Fangio said the 49ers could even use a platoon system.

The team will likely decide after the preseason on what approach to take.