Seahawks rookie defensive end L.J. Collier left Tuesday's practice with an ankle injury, and the first-round pick could be out for a little bit thanks to what head coach Pete Carroll described as a "rare sprain."

"He's got a badly sprained ankle, and it's going to be a little bit," Carroll said. "It's unfortunate. It was really an awkward position that he got tangled up in. We'll have to take some time to figure it out, it's going to be some weeks though."

Asked about preseason games for Collier, Carroll said. "We're going to take it one week at a time."

Carroll said that this particular sprain is unlike ones they're used to seeing, part of why the Seahawks will take a cautious approach with Collier.

"It's a little bit unusual, kind of the upper part of his foot," Carroll said. "It's an unusual one for us, we really haven't had a guy who sprained his ankle just like this. We're going to be really slow to make sure we know what we're doing with this. It's a rare sprain."

In other injury news, Mike Iupati sat out again with a foot sprain, but Carroll noted that the veteran left guard should be back soon and is no longer in a walking boot.

"Mike had a mild sprained foot, and he's doing great, it shouldn't be too long," Carroll said. "It's keeping him out right now, but he's in pretty good shape, he's out of the boot and all that kind of stuff already, so he's doing well."

Tight end Justin Johnson, an undrafted rookie out of Mississippi State, went down late in practice with what unfortunately appeared to be a significant injury.

"I'm afraid that he might have got an Achilles today," Carroll said. "Just one of those freaky injuries, he's out in open space, takes a step and that pop happens… It's very unfortunate."

Tyler Lockett gave fans a scare when he landed hard trying to secure a leaping grab, but he later returned to practice, and Carroll said the receiver, "got the wind knocked out of him."

Left tackle Duane Brown was absent dealing with a family matter. George Fant took Brown's place with the first-team offense.