ALAMEDA, Calif. -- Jack Del Rio began warning his Oakland Raiders' defense early about Ben Roethlisberger.

The big, strong Roethlisberger is known in league circles as one of the premier quarterbacks at extending plays. Finishing plays against Roethlisberger and not allowing him to spin away from sacks and from trouble, in general, will be paramount for the Raiders when they play at Pittsburgh on Sunday.

"He is so good at extending plays," Del Rio said. "It'll be an all-week emphasis."

Oakland cornerback David Amerson confirmed that containing Roethlisberger will be crucial.

"We've been talking about it," Amerson said. "We have to lock down our guys for the whole play. We have to make sure Ben is not extending the play. You have to keep your head on an extra swivel with him."

In others Raiders' notes:

• Pass-rusher Khalil Mack did not practice Wednesday because of a hamstring injury. He was banged up late Sunday, but after the game, Mack said he was fine. He was seen walking around the locker room Wednesday without much issue. Mack said on SiriusXM NFL radio Wednesday night he will practice Thursday.

• The Raiders signed returner Marcus Thigpen to replace Walt Powell, who was cut Tuesday. Thigpen, 29, was most recently with Indianapolis. Oakland is looking for a true returner to emerge. Powell was on the roster for two games, but didn't suit up.