DeCastro, the rookie, will have a more difficult task of it than Mendenhall, at least according to Mendenhall's wildly successful replacement, Jonathan Dwyer.
"Rashard's been here, he's earned a starting job, he's played well, he's had great years here. He starting and that's it," said Dwyer, who's given the Steelers back-to-back 100-yard games for the first time since early in the 2008 season.
Is this what Dwyer has been told by coaches?
"No one's said anything to me, but he's been the head honcho," Dwyer said. "He hasn't done anything wrong for him to have his job taken away from him. He's played well. When Rack's back, Rack will be the starter."
While Dwyer sat out of Wednesday's practice with a strained quadriceps, "Rack" Mendenhall returned for limited work after missing the last two weeks with an Achilles' injury that's most likely an offshoot of his Jan. 1 ACL injury.
Mendenhall came back from that injury Oct. 7 and gained 101 all-purpose yards in a win over the Philadelphia Eagles. He started the next week at Tennessee but left the game with the latest injury after 6 carries for 6 yards.
Dwyer started the next two games and rushed for 122 and 107 yards in wins over Cincinnati and Washington. It was the Steelers' first two-game win streak of the season and a physical and fast running game was a big part of the reason. That's why the Steelers won't rush DeCastro back either.
"First he has to get healthy all the way," center Maurkice Pouncey said of DeCastro. "And whenever he comes back he has to compete for a position just like anybody who's been off with an injury that long. And really it's going to be hard to take Ramon out of the spot with him playing so well."
The offensive line, with Ramon Foster holding down the right guard position that had been destined for DeCastro back in training camp before his knee injury, has played perhaps its best two games since Alan Faneca, Marvel Smith and Jeff Hartings were all here and healthy.
Would the Steelers break up this budding chemistry for a rusty rookie?
"I'm not worried about playing. I'm worried about getting the knee healthy," said DeCastro, who can begin practicing as soon as he's ready. After that, the Steelers would have three weeks to activate him.
DeCastro wouldn't give out the rest of his recovery schedule, but said "It's all right. Nothing good; nothing bad. I don't know what to compare it to so it's hard to judge how I'm doing. I think I'm doing well."
So is the offensive line. With 307 rushing yards (5.5 avg.) and only 3 sacks of Ben Roethlisberger in the last two games, the future is right now.
"We know the draft picks are made for a reason," said Pouncey. "But at the end of the day they're going to have to go in there and battle it out. And nobody's going to give up nothing."
NOTES – Troubled rookie nose tackle Alameda Ta'amu returned to practice Wednesday. The Steelers made room for him on the roster by releasing safety Damon Cromartie-Smith. … SS Troy Polamalu (calf), RT Marcus Gilbert (ankle), OLB LaMarr Woodley (hamstring) and ILB Stevenson Sylvester (hamstring) also missed practice.