Buenning was a fourth-round draft pick in 2005 and started 23 of 25 games he played in three seasons with Tampa Bay.
Mahan, who started 16 games at center for the Steelers in 2007, was a fifth-round pick of the Bucs in 2003. He appeared in 57 games, including 36 starts, for Tampa Bay from 2003-2006.
Pittsburgh received an undisclosed pick in the 2009 draft.
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