OWINGS MILLS -- The Baltimore Ravens have ruled out two-time Pro Bowl tight end Todd Heap and safety Tom Zbikowski for Sunday's game against the New Orleans Saints.

Heap has a pulled right hamstring, and Zbikowski has a back injury.

With Heap out for the second week in a row after getting hurt against the Pittsburgh Steelers, rookie Ed Dickson will make his second NFL start.

"I think it looks bad for Zibby," Ravens coach John Harbaugh said prior to releasing the injury report.

Harbaugh indicated that Zbikowski, who's awaiting results from a magnetic resonance imaging exam, could possibly be placed on injured reserve if he can't return in the next week or two.

"I don't think so, but when you've got a back you just have to see," Harbaugh said. "He's got an MRI coming back on that. We'll just have to see. There's not that much season left.

"If it's a couple, three week thing, then we're just going to put him down. If he can get back next week or the week after, then obviously we'll bring him back. I would say it's up in the air right now."

Zbikowski started the first six games of the season while safety Ed Reed was on the physically unable to perform list.

Now, Zbikowski's season is in danger.

"Here's a guy that played so well, then boom as soon as Ed came back, he got hurt," Harbaugh said. "Maybe it's fortuitous the way it worked out in that sense, they weren't hurt at the same time. Really tough on Zibby, just so disappointed for him because he was doing so well."

Meanwhile, running backs Le'Ron McClain and Willis McGahee are dealing with illnesses and are listed as questionable.

"Both got sick, so they couldn't practice," Harbaugh said.

McClain has written on his Twitter account that his stomach is killing him.

Cornerback Fabian Washington (hamstring), linebacker Tavares Gooden (calf) and wide receiver Derrick Mason (ankle) are all listed as probable.

All three players participated fully in practice Friday. It was Mason's first practice of the week after twisting his ankle against the Houston Texans.

The Saints ruled out wide receiver Courtney Roby (concussion) and tight end David Thomas (concussion).

Running back Chris Ivory (hamstring) is questionable. Defensive lineman Anthony Hargrove (knee) is questionable.

Middle linebacker Jonathan Vilma (quadriceps), offensive tackle Zach Strief (knee), tight end Jeremy Shockey (groin), cornerback Tracy Porter (shoulder), safety Malcolm Jenkins (rib), offensive tackle Jermon Bushrod (ankle) and defensive tackle Remi Ayodele (ankle) are all listed as probable.