Cardinals safety Tyrann Mathieu in action against the Seahawks.

Tyrann Mathieu was on the practice field Wednesday, and there is optimism he can be back from a shoulder injury on Sunday against the Vikings.

But being "back" is a relative term.

The Cardinals' safety has only missed one game this season – last week against the 49ers – and yet has not made nearly the impact he did a year ago. The main issue, of course, is his right knee, which has not fully recovered from last year's torn ACL and has bottled his explosiveness. Now, add the shoulder ailment to the list.

Mathieu went through a similar season in 2014, when he returned slowly from a late-2013 ACL tear and then broke his thumb. In effect, it was a lost year for him.

Cornerback Patrick Peterson believes that experience has helped Mathieu persevere this time around. Mathieu isn't so sure. He yearns to return to his playmaking ways.

"From the outside looking in maybe, but it's frustrating on the inside, obviously," Mathieu said. "A lot of noise. You try to tune that out."

There have been two contrasting Mathieus on the field during his four years with the Cardinals -- the healthy one and the recovering one.

In 27 games at full strength, Mathieu has been fantastic, registering 145 tackles, seven interceptions, two sacks, two forced fumbles and 26 pass deflections. His coverage when healthy has been air tight, and his versatility in the slot gives him the ability to impact games in multiple ways.

But he has also missed eight regular season contests, and in the games where knee and thumb injuries have lingered, Mathieu has been pedestrian. In those 21 contests, he has 63 tackles, two interceptions, seven pass deflections, a forced fumble and a fumble recovery.

Mathieu is on recovery road again, as a shoulder harness will be needed if he plays Sunday, while the knee remains an issue.

"He just can't seem to catch a break," Peterson said. "But Ty understands how to get his body back in the best shape and the best position possible to make sure he's ready to go on Sunday. That's never been a question.

"It's just something he's got to work through. As tough as it is and as cruel as it sounds, at the end of the day, football players are never playing at 100 percent, so you need to find a way to improvise through those injuries. He's a good enough player to do that."

It has been 11 months since the fateful ACL tear against the Eagles last December – Mathieu, appropriately, picked off a pass on the play – and it's realistic to think a breakthrough could be imminent. The shoulder injury seems manageable, and the knee brace is close to coming off.

Mathieu said he would meet with his doctor immediately after speaking to reporters on Wednesday, where he planned to make his plea to ditch the brace.

"Of course I'd rather play without it, but I don't want to do anything that puts me in harm's way," Mathieu said. "I'll talk to him, and I'm sure we'll negotiate something."

No knee brace could unleash Mathieu mentally as well as physically. Coach Bruce Arians is hopeful his star defensive back returns to form sometime in the next few weeks. Peterson is adamant it will happen.

"The guy, for crying out loud, before he came here (as a rookie) he missed a whole year of football and was an impact player instantly," Peterson said. "There's not a doubt in my mind. The confidence will always be there that he will be making those plays that we're accustomed to seeing him make."

Mathieu's football career has run the gamut, peaking as a Heisman Trophy finalist and NFL All-Pro and bottoming out with two major knee injuries and a dismissal from LSU. He's a natural optimist, but like anyone going through tough times, has bouts of frustration.

Everyone wants the Honey Badger back. Only time will tell if he can shed the injuries and summon that player in 2016.

"Life is frustrating sometimes," Mathieu said. "You've just got to deal with it. Can't get too high or too low. It's just another challenge for me. I embrace all those challenges."