Former Bengals full back Naufahu Tahi was a practice squad player, before the Minnesota Vikings signed him off the roster in 2007 and has played in 26 of 32 games since. Tahi is the lead blocker for the one of the league's most dangerous and entertaining weapons, Adrian Peterson.
Because of all the above, the Bengals are inviting the restricted free agent for a visit on Thursday. He is the second unconfirmed fullback that will be visiting the team in the upcoming week; the other being John Kuhn, who is also a restricted free agent, is the other. However, since both full backs came into the league as undrafted free agents, the Bengals won't have to give up compensation.
Regarding Tahi, I have very little information on his stint with the Bengals in 2006. In the second half against the Indianapolis Colts, I wrote, "While the line continues to dominate, Naufahu Tahi is punishing (and I mean PUNISHING) defenders. I'm not sure if the Colts depth is really this bad, or if Tahi (a TRUCK) is that powerful. He gained 10-yards, with 3 guys tugging at his back." The only other note I have of Tahi is when the practice squad was announced.