Halapoulivaati Vaitai replaced the 27-year-old Johnson and promptly surrendered a sack to Julius Peppers on the first drive.
Running back Wendell Smallwood also returned to practice Tuesday after sitting out the last two games with swelling in his knee. The 23-year-old Smallwood has been effective when healthy in place of the injured Darren Sproles, who is lost for the season.
"Working my way back. I felt good today," said Smallwood, who has rushed for 113 yards on 29 carries with a touchdown this season.