Steelers free safety Ryan Clark was cleared to play Wednesday after suffering his second concussion in 16 days. (US Presswire)

FS Ryan Clark was cleared to practice Wednesday, but he and the Steelers’ medical staff decided an extra day of rest could hurst less than 48 hours after suffering his second concussion in 16 days.

He anticipates final clearance to play Sunday night against Baltimore will come before practice Thursday.

“Everything’s good,” said Clark, who practiced on a limited basis. “I did well on the impact test, so we will see how it goes from here.”

Clark is optimistice about his prospects for playing Sunday against the rival Ravens. But he isn't so sure about the longterm future given his multiple concussions.

“Oh, I’m going to be messed up,” Clark said.

He said it with a smile, but Clark also acknowledged, “That’s just part of it,” when asked if he’s worried about the long-term effects on his brain.

“When you sign up to play this game, we know that there are risks and you know you pray and hope that you never have to deal with the long-term effects of it,” Clark said. “But you know there’s going to be long-term effects when you play a collision sport for a living. And you try to do the things to help combat that so you can have the best quality of life once it’s over.”

Clark cannot play in Denver because of the sickle cell trait he has that makes it dangerous for him to play in high altitudes. Other than games missed there, Clark has not sat out a game due to injury since 2008.

Mendenhall returns to practice: The Steelers’ four-game winning streak has coincided exactly with RB Rashard Mendenhall being out due to an Achilles injury. With that streak on the line Sunday, they might just have their starting running back available.

Mendenhall practiced fully Wednesday, the first time since being knocked out of the Oct. 11 game at Tennessee, in which he was held to 6 yards on six carries. In his only other game, he had 101 yards in a victory over Philadelphia. 

Other injuries: LB Stevenson Sylvester was a full participant in practice after missing the past two games with a hamstring injury. CBs Ike Taylor (illness) and Curtis Brown (quadriceps) were limited in practice. OT Max Starks (ankle) and DE Brett Keisel (shoulder) did not practice Wednesday, but their injuries are not considered significant. LB Chris Carter (abdomen) also did not practice.

The star trio of QB Ben Roethlisberger (shoulder/ribs), S Troy Polamalu (calf) and Antonio Brown (ankle) did not practice again. None are expected to play Sunday -- Roethlisberger has already been ruled out, but Brown “left the door ajar," as coach Mike Tomlin might say.

“This is one of the most looked-forward to games on the schedule,” Brown said. “The game that sets us where we’re going to be in the division. You always want to make a comeback against these guys, so I’m doing everything I can to get the necessary treatment to make sure I can go.”

Follow Steelers reporter Chris Adamski on Twitter @CBSSteelers and @BuzzsawPGH.