PITTSBURGH — Heath Miller, yet to practice with the Pittsburgh Steelers, took the next step in the rehabilitation process after right knee surgery some eight months ago when he was taken off the physically unable to perform list.

The nine-year veteran tight end, who tore three ligaments in his right knee against Cincinnati last December, called the move a step in the right direction. He remains vague about a possible return date: The Steelers open the season hosting Tennessee on Sunday.

“My mindset’s not going to change,” Miller said Monday. “I just want to keep improving each day and keep stacking those good days together. I still want to think short term, so that’s day by day, and keep getting better. That’s brought me to this point, and that will take me to a good point soon.”

He left it up to Steelers coach Mike Tomlin to determine when Miller can put the pads on. The two-time Pro Bowler, however, remains steadfast that he has never looked beyond incremental improvement.

“I feel good, and I’ve worked hard to get to this point,” Miller said. “Hopefully, I can take these last few steps. Fortunately, the timing of the injury was pretty good, because I don’t feel like I missed as much as I could have if I would have had to sit and watch through a whole season.”

Still, Miller anticipates a bit of a learning curve after sitting out training camp and each of Pittsburgh’s four exhibition games.

“I did have to miss the preseason, which is never fun when you’re not out there with your team, but I know that I’m closer to the end than the beginning,” Miller said. “So, that’s a good thing.

“As I’ve said all along, and I’m not lying to you guys, I’ve just tried to take each day (and) get better, and I knew if I did that it would be a good outcome, whatever that was.”

Miller’s even-keel approach and tireless work ethic has rubbed off on his teammates, particularly fellow tight end David Johnson. Johnson missed the 2012 season after right knee surgery and was taken off the PUP list several weeks ago, but spent time working alongside Miller as they moved through the final stages of rehabilitation.

“It’s getting a whole lot better, and I think it’s going pretty good,” Johnson said. “I’m just blessed to be back out here and working. It’s been a long road, but it’s feeling good. And every day it’s getting a whole lot better, and my running and blocking is getting a whole lot better every day as well.”