It's absolutely incredible perseverance to see from Desharnais. Down the stretch of the season the Oilers are going to need his physical play as games become more competitive, and of course as a kid from Quebec, Desharnais wants to get in the lineup against the Canadiens.
The Oilers medical team apparently only pulled Desharnais as a precaution, and were able to splint up his finger well enough now that he can not even miss a step. A broken finger usually takes 4-6 weeks to heal, so it's safe to assume this might be his pinky finger, and the Oilers medical team is able to significant reduce the pain which will allow him to play.