GLENDALE, Ariz. -- Shaq Riddick's return from his second hamstring injury of the offseason has been a gradual progression.

The Arizona Cardinals rookie linebacker eased back into practice Monday but began getting significant reps Wednesday. By Thursday, Riddick sped himself up a little.

"It's a process," Riddick said. "I didn't slam on the gas the first day. I wanted to see where I was at. Today, it's my second day. I actually put more of it to the gas pedal so it's just a progression because hamstrings ain't nothing to play with."

Taking it slow is understandable for someone who's had two hamstring injuries in four months, Cardinals coach Bruce Arians said, but Riddick doesn't have much time to make up for missing almost all of OTAs and minicamps, and the first three weeks of training camp. The Cardinals have their last two preseason games Sunday and Thursday before deciding who makes the final 53-man roster by Sept. 5. If he's allowed to, Riddick plans on playing in both games.

The 6-foot-6 outside linebacker isn't concerned with his standing on the team. He knows he's behind -- far behind -- when it comes to field activity. For the last four months, Riddick has been in meetings and studying his playbook, and getting mental reps during practice, so his understanding of the scheme is on par with every other defender. But the most physical activity he's had before this week was in the Cardinals' weight room.

The fifth-round pick is not lost on the field. Just rusty.

"This is my second day with a pair of shoulder pads on," he said. "Of course I'm behind. I'm at the bottom of the depth chart. I'm just blessed to be out here."

Getting healthy means getting back his "groove to rushing the passer."

Riddick has been staying after practice and working against the Cardinals' young tight ends to get back into playing shape. The work is starting to pay off, Arians said.

"He shows what we drafted -- big, tall guy that can really run and come off the edge," Arians said. "He's got some good strength at the point of attack, which should be his forte because he was a down lineman. But it looks like he can handle the sightlines of an outside linebacker. Pretty bright guy."

Coming off the field after Thursday's practice at University of Phoenix Stadium, Riddick couldn't contain a smile.

It's been a long time since he was healthy enough to run, nonetheless practice. Standing on the sideline, watching his fellow rookies, like defensive tackle Rodney Gunter and wide receiver J.J. Nelson work their way into the starting lineup, hasn't been easy on Riddick.

"It's terrible. It's the worst thing ever," he said. "You can't practice. You feel like you're on the outside of everything. You got all the vets and all the older guys nagging on you because you ain't playing, especially in my case because I was dealing with this in the spring, too.

"So, I haven't shown anybody anything for me to even be on this team or on this field with all these good players. The worst part about the being hurt part, to me, is not being able to show that I'm meant to be here."

It's taking him a while to get to full speed but Riddick is slowly getting there.