While currently a member of the best baseball league in the world, he might not have been the best player from the beginning. He didn't always show best performances, despite being recognized as the most powerful closer now. Occasionally, he struggled with ball controls, and gave a number of walks, critically led his team to dramatic(or traumatic) defeats. Moreover, when he was in national team, he showed bad performances and errors, such as limping right in front of the 1st base, so he faced criticism from all the Korean baseball fans.