NAPA, Calif. -- Antonio Brown, who has missed a significant portion of his first training camp with the Oakland Raiders, visited a foot specialist Saturday, a source confirmed to ESPN.

The injury is not believed to be long-term, and Brown could resume practicing as early as this coming week, a source told ESPN's Adam Schefter.

Brown, 31, who began camp on the non-football injury list due to what sources told ESPN were sore feet, participated in a pre-practice walk-through last Sunday and was limited in practice Tuesday. That night, he posted a picture of the bottom of his feet that showed them blistering and peeling. The team was off Wednesday, and Brown was not seen on the practice field Thursday, Friday or Saturday.

Raiders coach Jon Gruden acknowledged Friday that he was getting frustrated with Brown, whom the team acquired in the offseason, not being available.

"I think we're all disappointed," Gruden said. "We think he's disappointed. We'd like to get the party started. We'd like to get him out here. He's a big part of the team.

"I want the guy out here as soon as possible. I'd like him to never leave and stay in the huddle every play. But life goes on and you've got to continue to work, and the other guys got to take advantage of these opportunities, and so far, they have."

Raiders quarterback Derek Carr said Saturday he anticipated the chemistry he built with Brown during the offseason would return as soon as the receiver came back to practice.

"We wish that the healing process of whatever's going on be fast," Carr said. "We want it to be fast, but at the same time you can't rush things for training camp when you know you have a season and, hopefully, a playoff run to think about."

Carr said he had not seen the picture of Brown's feet. When shown it after his media session, he recoiled.

"We just know that when he does show up, we can't wait to welcome him with open arms, hopefully healthy and just ready to hit it running," Carr said. "We had so much time in the offseason, we spent a lot of time at my house, throwing. We spent hours upon hours throwing. So there is chemistry, there is development. I'm used to throwing him the ball, so it won't be brand new when he shows up. It will be just more on him, and the details of the routes, getting out and doing it and correcting it on film and going and fixing it the next day. Those kind of things. But besides that, the timing aspect, the meat and potatoes, so to speak, of what we need is there."