I'm a high school soccer coach, and one season, my senior captain tore his miniscus in the first game of the season. His doctor told him he could have surgery and end his season, or play through the pain and have the surgery afterward. He decided to play through it (pretty tough kid). It obviously affected him, but was able to play pretty well. Our physical trainer at school then told me that at her previous job, a senior football player played 4 games with a partially torn ACL, and had surgery after the season.
If I were Pierce, and I could handle the pain, I'd try to play. There is no guarantee he'll ever get to the finals again.
However, who could blame him if he sat out?