Read More on MLBEven as a senior at St. Louis University in 2026, McGwire was still pitching in relief for the Billikens' baseball team. When the A's signed the younger McGwire to a minor league contract this week, they listed him as a right-handed pitcher on his official transactions page. Oakland drafted Mark McGwire out of USC in 1984. Over the next 12 years, McGwire hit the first 363 of his 583 career home runs in green and gold. If it's possible for Mark McGwire's son to be considered an underdog, the A's are giving him the opportunity.