Packers coach Mike McCarthy said today that the knee injury sustained by projected starter Vernand Morency was worse than the team's medical staff originally thought, and that he now expects Morency to be out "a couple" of weeks.

The good news: McCarthy said Morency probably won't need arthroscopic surgery.

"I don't think so, no," McCarthy said. "(Team doctor) Pat McKenzie just thinks it's a little more serious than he initially thought. Just like I said, it's going to be maybe a couple weeks."

Morency injured his knee in the Packers' first training camp practice on Saturday. He wandered the sidelines without pads in the today's afternoon heat.

McCarthy originally said he expected Morency's availability to be determined on a day-to-day basis — a sign the team didn't think the injury was that serious. But now Morency is almost certain to miss the Packers' first preseason game, Aug. 11 in Pittsburgh.

McCarthy wouldn't go into detail about the extent of Morency's injury.

"If Vernand wants to share the details of his injury, he can go for it," McCarthy said.

Morency made a brief appearance in the locker room this evening, but declined comment and left for medical treatment.

McCarthy said Morency and the team weren't even sure which of two back-to-back plays he was injured on.

"I think it happened on one of those two plays. He's not really sure when it happened," McCarthy said.

Morency, a third-year player obtained when the Packers traded Samkon Gado to Houston last year, was expected to take over as the team's starting running back after Ahman Green signed with the Texans in the offseason.

But the Packers already were planning to use multiple backs in the position this season, and Morency's injury will give McCarthy a chance to take a closer look at the Packers' other options.

That includes rookie Brandon Jackson, the team's second-round pick out of Nebraska. The Packers' running game has looked sluggish in the first few days of camp, but Jackson already is showing his ability to catch the ball out of the backfield.

"I think he's doing well," McCarthy said. "He's getting a lot of reps, which is only going to help him. He's a gifted young man physically. He has the power and the quickness. ... He's feeling his way on some things and he's only going to get better."

Jackson said his first few days in an NFL camp have been a "little rocky," but says he is feeling more comfortable every day.

"It's a better opportunity for me because he's down right now," Jackson said. "But I've just got to take advantage of my opportunities that I have."

While Jackson is bound to draw attention as a high draft pick, McCarthy has been impressed with returning veteran Noah Herron.

"Noah has been very solid," McCarthy said. "I think he looks great compared to where he was at last year, too. So I think Noah Herron is a guy we don't talk a whole lot about that's having a very good camp."

Herron said he has an advantage because he's familiar with the system, but he expects all the running backs to get a closer look before Morency returns.