Kirk Radomski does not like Mike Piazza.
That said, according to his book, Bases Loaded, Radomski was asked by Mitchell investigators what he knew about Piazza. Radomski has no first hand information whether Piazza used roids, HGH or other PED's. Radomski writes that "Piazza is one guy I would have been happy to give up."
Radomski's opinion in analyzing Piazza's body visually was that he looked like someone who was roiding. Again, he has no firsthand knoeledge, just stating his opinion. After the fallout from Piazza's return to New York to open Citi Field and relectuance to address the media, Radomski's opinion could very well be spot on.