As a flip side to the other thread, I thought this was a good idea.
Name one player who outperformed your expectations of them either when they first signed or from their early form. Paul Walsh, always rated him right from his Chalton Athletic days but thought he was passed it when we got him. Turned out to be quality and only wish he'd stuck around a bit longer.
Mine (and I suspect many other's) would be Pablo Zabaleta. Early on I just thought he was a headless chicken and totally rash; two yellow cards waiting to happen. Nine years later he leaves as a club legend who embodies nearly everything I love about my club and he put his all in at all times.