SPARTANBURG, S.C. – Upon further review, the little things were what loomed large for head coach Ron Rivera in the Panthers' preseason opener.

"There were some really good things. The biggest disappointment, just like I told you guys that night, was not scoring a touchdown with the first bunch," Rivera said after reviewing game film of Carolina's 22-19 loss at Baltimore and returning to training camp.

While pleased with the first-team offense marching nearly the entire length of the field, Rivera broke down what stood in the way of finishing the job.

"We drove down in the red zone and then we missed a couple of blocks on runs," Rivera said. "Then Teddy (Ginn) wasn't the primary receiver and assumed the ball had been thrown. Then Cam (Newton) made the decision to throw to him, and if Teddy had just kept going, it would have been a touchdown."

Rivera was mostly pleased with the defense but called the tackling "spotty" as well as the performance on third downs as the Ravens converted half of their chances. He also liked the debut of the rookie cornerbacks overall but again saw room for improvement.

"They did a nice job. I would have liked to have seen them challenge a little more, but that's something they'll get more and more comfortable with," Rivera said. "They did some nice things. They showed their willingness to tackle."

Wide receiver Brenton Bersin, who suffered a rib injury in the game, is "bruised and sore" Rivera said. Bersin sat out practice, as did fellow receiver Philly Brown, who came out to practice but felt sick and went back inside on a sweltering day.

"Maybe too much lunch," Rivera said.

Tight end Ed Dickson, safety Dean Marlowe, linebacker Ben Jacobs, defensive ends Rakim Cox and Larry Webster, wide receiver LaRon Byrd, fullback Devon Johnson and cornerback Leonard Johnson also sat out practice.

Defensive tackle Ray Drew, signed Friday to fill the 90th roster spot, practiced for the first time. The University of Georgia product was an undrafted rookie in 2015.