Cardinals RB David Johnson shows off his pingpong skills at a tournament with the Boys & Girls Club. (1:10)

PHOENIX -- Now that his cast is off, Arizona Cardinals running back David Johnson has begun rehabilitating his injured left wrist, but early returns this week show it’s going to be a long process.

“I’m pretty stiff,” Johnson told ESPN. “I’m still getting the range of motion.

“Still pretty weak, but I’m making progress.”

Johnson, who suffered what he described as a ligament tear in Week 1, still wasn’t able to put a timeline on his return. His doctors told him that recovering from wrist injuries can be unpredictable, but Johnson said he hopes to return “soon.”

Before Johnson can think about that, though, he has to be able to move his wrist well enough to both carry and catch a football. That’s in addition to regaining his confidence.

If he doesn’t return to the Cardinals in 2016, the 25-year-old All-Pro said he will feel as though he “wasted a season.

“A season where I could get better, help out the team especially,” Johnson said. “I feel like I let the team down, let a lot of people down. I’m going to be down on myself, for sure. It’s going to really motivate me in the offseason again because I had the knee injury [at the end of last season].

“I was excited to come back this year.”

In the meantime, Johnson said he’s glad to hit his rehab work. The cast, which he had removed Monday, “was getting annoying,” and not being able to move his wrist was no fun. He still has stitches in, which will also lengthen his timeline.

Still, Johnson said, the goal remains the same: "Get back as soon as I can.”