I would find out whether its due to his/ her will or skill. If its will, Id set up and one to one meeting and set some small goals along with long term goals. If i see any changes towards the eagerness Id support him/her 100% but if I find out that he/she is not happy Id go down the HR path. But it was his Skills, I'd analyze his/her performance to find out where he needs more support and training and that way I help him to get over that issue/ obstacle. Periodically I review his performance to see whether he/she had mastered the task or not. I hope it helps