GLENDALE, Ariz. -- Tyrann Mathieu, Justin Bethel and Frostee Rucker practiced for the first time this training camp Sunday and Arizona Cardinals coach Bruce Arians said "there's no doubt" all three will be ready for the Sept. 11 season opener.

Mathieu, an All-Pro safety last season, is coming back from surgery to repair a torn ACL. The cornerback Bethel is returning from foot surgery and defensive lineman Rucker had a foot injury that may have been related to offseason ankle surgery.

Arians also welcomed back wide receiver John Brown, out with a concussion since early in camp.

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And the coach said outside linebacker Alex Okafor had decided to keep playing despite a torn biceps tendon rather than opt for surgery.

Mathieu returns a much wealthier "Honey Badger" after he signed a six-year $63 million that included $21.5 million guaranteed and another $18.75 million guaranteed if he's on the roster at the start of the 2018 season.

The do-everything player is listed as a safety but played more snaps at cornerback last season before he went down with the knee injury on Dec. 20. It was his second significant knee injury in his three NFL seasons. He sustained an even more severe injury to his left knee in his rookie season.

Despite that, the Cardinals wanted to lock up a player whose passionate play rubs off on his teammates.

"I wouldn't say his passion's coming back yet, but having him out there in the huddle, it's going to be good," Arians said. "... It takes a little time to get in passion shape."

Bethel, a three-time Pro Bowl selection on special teams, started four games at cornerback last season and was considered a leading candidate for the job this year opposite All-Pro Patrick Peterson. But, in Bethel's absence, the job has gone to rookie Brandon Williams.

Williams struggled in his first preseason game but was noticeably improved in Friday night's 19-3 loss at San Diego. Arians said Williams also showed improvement in the team's two joint practices with the Chargers.

"I thought Brandon got really better last week," Arians said before practice Sunday, "going against different receivers, seeing different things. I thought he held his own all week."

Mathieu, Bethel and Rucker came off the physically unable to perform list last week. Arians said the three would do individual work and then he'd see how much they could take part with their teammates in a regular practice.

Asked if he thought they'd be ready for the opener against New England, Arians said, "There's no doubt. It's just a matter of conditioning now, football conditioning, hit, getting the pad level down and all the things we've been doing the last 15-18 days."

Okafor, in the final year of his contract, missed nearly all of his rookie season with a biceps injury but came back with a team-high eight sacks in 2014. He got in the coach's dog house last season when he injured his toe during the team's bye playoff weekend and wasn't able to play in the postseason.

Brown, who topped 1,000 yards receiving last year, had been in concussion protocol since his head was slammed to the turf in the fourth day of training camp.

The task now, Arians said, is "to get him back in shape so he doesn't pull a muscle."

Arians said he was hopeful first-round draft pick, defensive lineman Robert Nkemdiche, would be able to practice some Wednesday. Nkemdiche has been sidelined with a high ankle sprain since rookie training camp four weeks ago.

The Cardinals have been outscored 49-13 in two losses this preseason but Arians brushed aside any concern. He was unhappy -- he used a stronger word -- with the offense's performance in San Diego after the game but didn't dwell on the subject on Sunday.

He considers "95 percent" of the team's problems Friday night to be easily correctable.

"Nobody's shaken in their confidence in any way. It's preseason," Arians said. "I think the tendency (of those outside the team) is `woe is me' but when our starters have played maybe 20 plays, that's not even a good half. We've had bad halves before and come back and won games. So it's not a doomsday situation by any stretch of the imagination."