Johnson, who underwent an ankle procedure in June to have it surgically cleaned out, declined comment to reporters but was heard yelling to receivers coach Mike Sheppard that he felt great.
"We're working him slow. He's got some things to work on," offensive coordinator Bob Bratkowski said, according to WLW-Radio in Cincinnati. "When you've been away from it, playing the real game out here is different than the rehab he's been doing. He's got a good start out of it. We're going to work him in slowly, bring him along a little at a time."
Bratkowski said it was possible the eighth-year, five-time Pro Bowler could play in Monday's preseason opener at Green Bay.
Johnson is coming off his best season statistically, having recorded a career-high 1,440 yards with 93 receptions for a 15.5 yards-per-catch average in 2007. He scored eight touchdowns.
"He looked good, he's got a lot of work to do to get back in shape and just get ready for the long season ahead of him," Palmer said, according to the station. "It's always good to get your returning starters, especially one of the best players on the team, get him working and get ready for the season."