Conversation so far:
Where was Mike Piazza born?
Mike Piazza was born in Norristown, Pennsylvania, grew up in Phoenixville, Pennsylvania
What were the names of Mike Piazza's parents?
Mike Piazza is the second-oldest son of Vince and Veronica.
How many siblings did Mike Piazza have?
Mike Piazza has four brothers Vince Jr., Danny, Tony, and Tommy
What school did Mike Piazza attend?
Mike Piazza attended Phoenixville Area High School
When did Mike Piazza start playing baseball?
Mike's father saw that Mike Piazza had potential in the sport, and began encouraging his son to build his arm strength at the age of five

Question: Who trained him as he was growing up?
Self-contained rewrite: Who trained Mike Piazza as he was growing up?