Lucas signed a reserve/future contract with the 49ers on Monday, per the NFL's official transaction log.
Lucas entered the league in 2014 but hasn't suited up for a game yet. The 49ers are his sixth team in that span. Even if he sticks with the team until Week 1 of the 2019 season, Lucas has a ceiling as a special-teams asset since second-year tight end George Kittle is a rising star who will command work on most pass-catching situations.