Raiders CB Shawntae Spencer (No. 36) sprained his right foot Sunday against the Dolphins and was on crutches Monday. (AP)

In their opener against San Diego, the Raiders lost starting left cornerback Ron Bartell for at least seven games to a broken shoulder blade.

Now they’re waiting to find out exactly how long they’ll be without starting right cornerback Shawntae Spencer, who sprained his right foot Sunday against Miami in the fourth quarter.

Spencer was on crutches and wore a walking boot on his right foot as he left the facility late Monday afternoon. He said he didn’t know how long he’d be out.

“We’ll see tomorrow,” Spencer said.

Raiders coach Dennis Allen said Spencer’s foot injury as well as starting right tackle Khalif Barnes’ groin injury are “probably significant.”

“I don’t know the exact extent of what those injuries are, but those are two guys who could potentially miss some time,” Allen said.

With the Pittsburgh Steelers coming to Oakland on Sunday, the last thing the Raiders could afford was to lose another cornerback. Miami rookie quarterback Ryan Tannehill and Brian Hartline torched the Raiders’ secondary, connecting nine times for 11 yards. Now the Raiders will almost certainly have to face Pittsburgh quarterback Ben Roethlisberger and explosive wideouts Mike Wallace and Antonio Brown without their top two cornerbacks.

Pat Lee started for Bartell against Miami but was replaced after one series by Joselio Hanson. Lee saw more playing time later, especially after Spencer was injured. Neither had much success covering Hartline.

“We’re going to look at the personnel that we have,” Allen said. “We’re going to look if there’s anybody out there that we feel like can help us. So that’s definitely a position that we got to look at and see where we’re at and see if there’s anything we need to do.”

The Raiders have two other healthy corners on their 53-man roster, Coye Francies and Phillip Adams. Adams, who was claimed off waivers Sept. 1, is primarily a punt returner. They signed Francies from their practice squad Saturday. Hanson signed with the Raiders Sept. 3 after being waived by Philadelphia. Neither Adams nor Francies took a defensive snap against Miami.

“Next guy has to step up, if that’s the case,” Hanson said. “That’s why you have depth on a team. In the NFL everybody can play, so the next guy has to step up.”

Chimdi Chekwa, a 2011 fourth-round draft pick, is another option. He’s was signed to the practice squad after being waived in the final cuts Aug. 31. The Raiders waived cornerback DeMarcus Van Dyke, a third-round pick last year, in the final cuts. He signed with Pittsburgh and will face the Raiders on Sunday.

After Barnes went out in the second quarter, Willie Smith took over and played the rest of the game. Smith, who signed with the Raiders on Sept. 1 after being waived by the Redskins, will start Sunday if Barnes can’t play, Allen said.

“I thought he did some nice things coming in, only being here for 10 days now,” Allen said. “We’ll continue to work with him. I feel like he’s somebody that we can work with that can get better.”

Smith started the final three games at left tackle last season for Washington, facing standout defensive ends Jason Pierre-Paul (Giants), Jared Allen (Vikings) and Trent Cole (Eagles) in succession. Each one had one sack.

“Willie’s an athletic guy, really smart guy,” Allen said. “He’s going to know what to do. He’s got all the tools to execute it. I have confidence in him.”

Follow Raiders reporter Eric Gilmore on Twitter: @CBSRaiders.