Chief Executive Stefan Gamble said: "On behalf of the Board we thank Sean for his time, effort and dedication during his short spell at the Club and wish him well for the future."
O'Driscoll added: "I am extremely disappointed for the players, their performances over the past month have not gained the points they deserved.
"This is a different phase of the season, and as we have repeatedly seen, teams have recognised the team’s strengths from the first half of the campaign and prepared to counter that when facing us.
"But the players deserve enormous credit for adapting, finding different ways to play and maintaining their performance levels even, at times, in the face of frustration and disappointment.
"They are a close group whose success so far has been built on the trust, understanding and respect among them. I wish them the best for the rest of the season."
The Club will be making no further comment.