BBC Sport's cameras witnessed how Sam Warburton suffered the knee injury that has ruled him out for up to six weeks.
He initially damaged the knee driving at the Ulster line, got up and then put in a tackle that seemed to exacerbate the problem.
Warburton stayed on until a break in play before being released in the 24-24 Pro12 draw on Friday, 7 April.
Highlights: Ulster 24-24 Cardiff Blues
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