He hasn't done any Killie games yet and it would seem that Saturday will be just his fifth ever SPL match, having started out in the SFL in 2005. He's only issued one red card so far this term, although his yellow card count seems to vary.
That's about all there is to go on this week. in SPL terms, Mr O'Reilly is pretty inexperienced and that's something that could well be moaned about by at least one manager after Saturday's game. Hopefully, for everyone's sake, he puts in a good performance.