Cornerback Jimmy Smith, Baltimore's first round selection in 2011, left practice early on Thursday with what potentially is a back injury.

Coach John Harbaugh normally addresses the media about injuries but was unavailable following practice. Defensive coordinator Dean Pees said he wasn't sure what exactly happened to Smith.

"He just went down," Pees said. "I know he grabbed his back but that's all I saw. I don't know any extent of it."

Smith hurt himself while guarding receiver Jacoby Jones on an inside slant. Smith was in front of Jones but stopped and kneeled to the ground. He got up but took only a couple of steps before falling down again.

Three trainers tended to him and one escorted him to the training room. Smith walked gingerly off the field.

Smith is competing for a starting cornerback position against Cary Williams. Both have been rotating at the spot in Baltimore's base package.

"It's great competition," Pees said. "We're very lucky to have two big guys like that fighting for that position. It's a luxury and a fortunate situation for us."

Holding his own: Kelechi Osemele, lining up at right tackle, kept rush linebackers from getting past him numerous times in one-on-one drills. With Sergio Kindle matched up against him, the rookie from Iowa State stonewalled him twice, not letting Kindle get past him.

Justin Tucker's day off: The Ravens rested rookie kicker Justin Tucker and had Billy Cundiff attempting field goals. Cundiff made six of his seven attempts. The roles will be reversed Friday, with Cundiff taking a day off and Tucker receiving all of the reps.

Stepping up: With Dennis Pitta out with a broken hand, Ed Dickson has received more looks from Joe Flacco at the tight end position. On Thursday, Dickson might've put in his best training camp practice. He outmuscled defenders on at least two catches and caught a touchdown down the seam with linebacker Dannell Ellerbe covering him.

Sitting out: Left guard Bobbie Williams didn't participate in Thursday's practice, but was on the field observing his teammates. Williams possibly sat out to rest his right ankle, which he broke last December. Defensive end Arthur Jones was also absent from practice for an undisclosed reason. Center Matt Birk sat out his fourth consecutive practice as it doesn't appear the Ravens have plans to use him often during training camp.

Still absent from practice: DT Haloti Ngata (hamstring), OLB Courtney Upshaw (shoulder), TE Dennis Pitta (hand), LT Bryant McKinnie (back), OL Jah Reid (calf), LB Josh Bynes (undisclosed), RB Bernard Pierce (hamstring), WR Tandon Doss (hamstring), WR David Reed (ACL), WR Patrick Williams (undisclosed).

Moving inside: The Ravens received an early present with practice moving to the indoor practice facility. The high temperature in Owings Mills, Md. was 93 degrees. Coach John Harbaugh, in a statement read by Ravens senior vice president of public and community relations Kevin Byrne, said he made the change to reward his players.

"We came inside to get out of the heat," Harbaugh said. "We've had outstanding work out in it since the start at camp and we changed it up today. I'm not sure it was because we came inside but we had a sharp, crisp, fast practice today. You can see the coaches are very pleased."

Follow Ravens reporter Jason Butt on Twitter: @JasonButtCBS and @CBSSportsNFLBAL.