Diaz went 2-for-4 with a homer and three RBI against Detroit on Sunday.
The catcher is set to start the season with Triple-A Indianapolis after Pittsburgh resigned backup Chris Stewart to a two-year deal. After slashing .312/.366/.421 in 404 minor-league plate appearances in 2014, he fell off last year (.271/.330/.382) and oddly made only two plate appearances as a September recall. The organization still values Diaz, however, as the Bucs reportedly turned down an offseason deal which would have sent the catcher to Texas in exchange for first baseman, Mitch Moreland.