Rice, who was geared up in cleats and gloves, helped the 49ers quarterbacks warm up by catching passes from them.
Rice also worked with the wide receivers during warm-ups.
It's not the first time that the 49ers have opened up practice to former 49ers greats. Legends such as former defensive lineman Charles Haley have also attended past practices.
The new 49ers regime, led by general manager John Lynch and head coach Kyle Shanahan, has been very open to honoring the team's rich history and has welcomed past greats to visit the team.
The 49ers acknowledgment of the past will also be evident at Levi's Stadium this season. The stadium will be adorned with banners throughout the concourse honoring past players and team accomplishments. The 49ers will also unveil the team's Ring of Honor at the stadium this season.