With Reggie Corrigan ruled out with a wrist injury, Marcus Horan will almost certainly come into the front row and Justin Fitzpatrick expected to be named on the bench.
However, it's what backline combination O'Sullivan will go with where main interest will centre. The options open to him at full back, wing and outhalf concern, Girvan Dempsey, Geordan Murphy, Shane Horgan, John Kelly and either David Humphreys or Ronan O'Gara at number 10.
Neither Dempsey nor Horgan played at the weekend but O'Gara did and he came through his club's encounter with UL Bohemians unscathed. Whether he will dislodge a player who has played a huge part in Ireland's two Six Nations wins to date remains to be seen.