It was previously unknown whether Troy Smith, a contender for the starting job in the preseason, would be able to compete with Flacco when Smith recovered from a tonsil infection.
But Harbaugh said yesterday that Smith would remain the No. 3 quarterback this week and would be able to vie this season only for the backup job, which is held by Todd Bouman.
"That'll be [Smith's] role this year - possibly into a role where he can contribute playing quarterback for us down the road," Harbaugh said.
The 29th-rated passer in the NFL, Flacco has completed 58.5 percent of his passes for 603 yards. He has thrown one touchdown and four interceptions.
Asked about his comfort level knowing he has the job, Flacco said: "That's the way I've been approaching it. [I try to] get better each week and go out there and help this team win."
Terry expects to play
Despite not practicing because of a knee injury, starting offensive tackle Adam Terry said he expects to play Sunday at Indianapolis.
"Spit on it, tape it up, rub some dirt on it, and we'll see how it goes," said Terry, who sprained his right knee late in the third quarter Sunday. "As of right now, I fully anticipate going out there and playing."
Two defensive starters - cornerback Samari Rolle (neck) and safety Dawan Landry (neck) - are out. Fabian Washington (shoulder), who is Rolle's replacement at cornerback, did not practice.
The players limited in practice were linebackers Ray Lewis (knee), Antwan Barnes (knee) and Tavares Gooden (hip), offensive tackle Jared Gaither (knee), running back Willis McGahee (knee) and safety Tom Zbikowski (shoulder).
Gregg on injured reserve
Ravens nose tackle Kelly Gregg was officially placed on injured reserve after having successful microfracture surgery on his knee.
"It went better than anticipated," Harbaugh said. "In other words, less work had to be done."
With Gregg done for 2008, Justin Bannan will start an entire season for the first time in his seven-year career.
"It feels good," Bannan said. "Obviously, you never want it to be because your friend gets injured. The main thing is coming out and helping the guys around me, making sure they can rely on me and trust that I can get the job done, too."
To fill Gregg's roster spot, the Ravens signed Brandon McKinney, a third-year defensive tackle who started two games for the San Diego Chargers last season. He was released by the Chargers on Saturday.
Ravens running back Le'Ron McClain is second in the NFL in fourth-quarter rushing with 141 yards. He trails only the Tampa Bay Buccaneers' Earnest Graham (172 yards). ... Former Ravens offensive tackle Jonathan Ogden has joined USA Football, the sport's national governing body on youth and amateur levels that conducts 100 annual football training events. ... Offensive tackle Joe Reitz, who is on the practice squad injured reserve list, had shoulder surgery Tuesday.