The full-back was led from the field in obvious pain, by Munster doctor Eanna Falvey and Cullen will undergo an MRI scan on Monday to ascertain the exact seriousness of the damage.
All in all then it was a miserable afternoon for the Munster side. In what was another flat performance they allowed the Blues boss and bully them around the park, gifted the home side a healthy lead and then came up woefully short in their efforts to play catch-up.
Given the level of their opening half performance it didn t look too bad when they went in at half time trailing by just eleven points (17-6). On two occasions in the second half they did manage to get back to within a score of the leaders but each time they ceded territory and a score. With the score at 13-20 Munster were pressing but a loose ball snatch led to a Cardiff break-out which resulted in a try at the other end.
Captain Frank Sheahan brought it back to a seven point game late on but once again with Munster on the front foot, precious ball was coughed up Cardiff broke out and when Munster were penalised a further ten metres for dissent, Lee Thomas smacked over the penalty that denied the visitors a consolation bonus point.
Munster. C Cullen (P Devlin); J Kelly, S Payne, R Henderson (J Holland), A Horgan; P Burke, M Prendergast (E Reddan); M Horan, F Sheahan, G McIlwham; T Bowman (A Quinlan), T Hogan; J Williams, D Wallace, S Keogh.