Staley missed three days of practice after having fluid drained from the knee Wednesday. He returned to practice Saturday, but didn't work much.
"We're going to be very proactive and make sure that if there are any problems that we get it taken care of now," said Steelers coach Bill Cowher. "We want him ready to go for the first game against Tennessee."
Haynes and Parker scored on runs of four and five yards in a brief goal-line session.
The goal-line drill is an annual camp highlight,, and an estimated crowd of 13,500 came to St. Vincent College to watch practice. But they saw only three plays in two goal-line series.
With the ball placed the 5-yard line, the first-team offense moved the ball a yard on the first carry against the first-team defense. Haynes carried behind fullback Dan Kreider and three tight ends – Jerame Tuman, rookie first-round pick Heath Miller and Walter Rasby.
On second down, Haynes found a hole left of center and burst four yards for the score.
The second series with the second teams lasted one play. Parker took a handoff, didn't see any daylight inside and bounced it around left end for a five-yard touchdown run.
"There wasn't really a hole there," said Parker, the second-year speedster. "That's why I had to do what I had to do and just get it in the end zone."
With Staley dealing with injuries, and Bettis hoping to enter the season as the second back, and even Haynes also dealing with knee problems, Parker could become the go-to back sooner than expected.
"Yeah, and that gives me a lot more reps and a lot more confidence," he said. "But they're alright. They're not really hurt. They're just taking some time off like vets do. They know how to use their body and they'll be back."
Parker was the surprise story of last year's training camp. Undrafted out of North Carolina in spite of 4.3 40 speed, the 5-foot-10, 209-pound Parker led the team in preseason rushing, but didn't play in the first seven games. He carried three times against the Philadelphia Eagles, and then carried eight times for 44 yards the following week at Cleveland. Parker had only two more carries the next six games before breaking out with 102 yards on 19 carries in the regular-season finale at Buffalo.
"Last year we felt good in the preseason but when we got in-season it was a different ball of wax," said Whisenhunt. "But now, after a year with Willie, you certainly feel more comfortable putting him in there."
"You can tell a lot about a player in the second year by how he works and how he prepares. Certainly being around Duce and Jerome and Verron has helped him as far as making sure you prepare the right way. Those are good models. He's taken it upon himself and he's done a good job."
Whisenhunt was asked if Parker gives the Steelers a different dimension from their other running backs.
"You know, I think Jerome may be a little faster than him," Whisenhunt said to a puzzled group of reporters.
"Certainly he does," Whisenhunt crowed a couple of seconds later. "He certainly gives you a little bit of a speed option. It's exciting when Willie gets into the open field, and he's doing a good job with his inside running, which is really exciting."
"I think Willie Parker's a very exciting prospect," said Cowher. "You can see the speed that he has. Noah Herron's done a very good job with all the additional opportunities he's received. It's going to be great to see these guys in preseason as well."
Will there be enough room on the roster for all of them?
"We'll find out," Cowher said. "I don't think you can ever have enough backs. It's a nice problem to have right now."