Cardinals safety Tony Jefferson celebrates a pass breakup in last week's win over the Packers

Tony Jefferson is the preeminent jokester on the Cardinals.

The third-year safety loves to stir the pot, and running back Kerwynn Williams freely admits he's one of the most common targets.

In training camp, Jefferson did an interview in which he dissected the ‘Madden NFL 16’ video game ratings. He intentionally brought up Williams' name to explain a 72 rating was quite generous -- that Williams' true talent level merited a 55.

"I've got to give him credit where credit is due on that, because I didn't even see that coming," Williams said. "He's like, 'Yeah, man, did you see that interview?' And I was like, 'No, let me check it out.' I should have known something was coming my way."

Jefferson can't help it. He knows there are times to be serious, but when it's not one of those situations, watch out.

"One thing my parents have always told me is to be me," Jefferson said. "I've always had a personality."

While Jefferson loves to jest, the start to his NFL career was no laughing matter.

Jefferson starred at the University of Oklahoma and left for the draft after his junior season because evaluations suggested he would be an early-round pick. For reasons he's still unsure of – a slow 40-yard dash time likely contributed – Jefferson wasn't selected, and it made his head spin.

"I never even had a vision or thought about not being drafted," Jefferson said. "It was a shock. I didn't really know what to expect. I was thinking my football career may slowly be coming to an end."

He latched on with the Cardinals for offseason workouts, not as a golden-child draftee but as a free agent trying to swim upstream. About a month in, coach Bruce Arians saw more potential in Jefferson than a run-of-the-mill undrafted rookie.

"He's a very instinctual player," Arians said. "He made up for the speed with his instincts, and once we put the pads on, he was a football player, a good tackler."

Jefferson made the team and was a backup as a rookie, and the past two years, he's played a vital role in a secondary.

He came up big in key spots throughout the regular season, finishing with 75 tackles, three forced fumbles, two interceptions – a pick-six against the Bears and a game-saver against the Ravens – and two sacks.

One of Jefferson's best games came against the Packers last week. He was one of four Cardinals to play every defensive snap and finished with a game-high nine tackles while adding two tackles for loss and a pass breakup.

 "You could say defensively he put the team on his back," defensive tackle Calais Campbell said.

Jefferson is still only 23 but has progressed as a professional. He said it's a completely different world compared to college.

"In the Big XII, we didn't really gameplan or anything," Jefferson said. "Read the card, and that's the defense we'll be playing. My mental focus was basically to just go out there and play what's called. At this level, you can't do that."

Cornerback Jerraud Powers said Jefferson has learned to balance his laid-back demeanor with hard work.

"When he first got here, he was a video game kid, if that makes sense," Powers said. "All him and (safety Deone) Bucannon wanted to do was play video games. But just being around some vets – Pat (Peterson), Rashad (Johnson), myself – and just seeing how the day-to-day grind is, as far as preparation and everything, it kind of wore off on him a little bit. He watches more film now than he had. He takes his preparation seriously."

It's not lost on Jefferson that he's a starter for one of the NFL's best teams, but no matter how much triumph he finds, the anguish from being undrafted never dissipates. Jefferson said he keeps tabs on every safety drafted in 2013 and he's constantly motivated to outperform them.

His jovial nature vanishes when it's discussed.

"That chip is still there, and it just grows as my game grows," said Jefferson, who will be a restricted free agent after the season. "It helps me have a purpose. I still feel like I'm the undrafted guy. Commentators, when they talk, they don't talk about me. They talk about everybody else. I'm still trying to build my résumé."

The Cardinals' 2013 draft class has resulted in some hits, but for this playoff run, Jefferson is shining brighter than all of those selections. Safety Tyrann Mathieu, linebacker Alex Okafor and guard Earl Watford are injured, while running back Andre Ellington, running back Stepfan Taylor and linebacker Kevin Minter are in platoon roles.

In Sunday's NFC Championship game against the Panthers, Jefferson will be counted on to contribute heavily. It's something no team thought he could do coming out of college, but three years later, the joke is on them.

"I knew all along I belonged, because I knew what the type of player I was, and what type of players that were drafted when I knew I was better than them," Jefferson said. "I never really doubted, but I didn't know how it worked. I didn't know, since I was undrafted, if I really didn't have a shot. Me and my agent, we didn't really know we were going to experience this, but we did, and I'm glad it's working out the way it is."