"He took all the reps today in our walkthrough," Gruden told reporters, according to ESPN's Paul Gutierrez. "He showed great retention and we'll see what happens here with this afternoon; we're going to have a walkthrough today as well. We have a lot of guys that can't practice so we'll pick it up tomorrow."
Asked if Brown was close to being a full participant in practice, Gruden said, "I think so, yeah."
Brown is dealing with frostbitten feet from a cryotherapy chamber mishap. He's yet to practice since the incident. The 31-year-old didn't suit up for Oakland's second preseason game but did run drills during pregame workouts.
The seven-time Pro Bowler is also in the midst of an ongoing fight to wear a helmet that's no longer approved by the NFL. His camp is currently searching for a Schutt Air Advantage model manufactured within the past 10 years.
Brown found a 2014 edition of his preferred model, but it failed a test required by the NFL and can't be used, a source told ProFootballTalk's Mike Florio.
Despite Brown's prolonged absence, Raiders quarterback Derek Carr was quick to point out how fast the star wideout has familiarized himself with the team's playbook.
"The man's recall is unbelievable," Carr said. "He came in and no mental errors, and in this offense, that's not easy to do. Especially whenever you have a day off ... you've got to stay on coach Gruden's offense all the time. You can tell Antonio's been studying because he came out and didn't miss a beat.
"He was a part of everything we did today."