O'Connell travelled with the squad to Wales yesterday but complained of the injury later that evening and Mick O'Driscoll was immediately summoned and arrived at the team hotel earlier today.
Donnacha Ryan will take O'Connell's place alongside Donncha O'Callaghan with O'Driscoll on the bench and the side will now be led by Ronan O'Gara.
O'Connell is expected to be fully recovered in time for the game next week against Perpignan.
Munster: P Warwick; D Howlett, J de Villiers, L Mafi, K Earls; R O'Gara, T O'Leary; W du Preez, D Fogarty, J Hayes; D O'Callaghan, D Ryan; A Quinlan, N Ronan, J Coughlan. Replacements: D Varley, T Buckley, M O'Driscoll, N Williams, P Stringer, I Dowling, D Hurley.
Ospreys: G Owen; T Bowe, S Parker, A Bishop, N Walker; D Biggar, L Davies; D Jones, R Hibbard, C Mitchell; A-Wyn Jones, J Thomas; J Collins, M Holah, F Tiatia. Replacements: H Bennett, P James, C Griffiths, A Lloyd, B Lewis, R Webb, J Hook.