"I watched him throw this bullpen, and all of a sudden I saw a ball that I hadn't seen," Gwynn said. "I was sitting down watching him, and I stood up and called over Rusty Filter, our pitching coach, and I said, 'What was that? Was that something different?' And he told me, 'He's working on it.' " So, what is this mystery fourth pitch? Gwynn is tight-lipped about the details, disclosing just two things: It's an off-speed pitch, and Strasburg learned it while pitching with the Team USA during the Beijing Olympics.