Lock Lewis Stevenson's late call-up to the Ulster squad suggests a big problem ahead of tomorrow afternoon's Heineken Cup clash with Montpellier (3.40pm).
With their French hosts boasting one of the biggest sets of forwards in world rugby – and a virtually impregnable home record - Ulster dare not take to the pitch with anyone less than 100 per cent fit. But disruption so late in their preparations is a headache they could have done without.
Captain and lock forward Johann Muller picked up a neck injury in the second half of last Friday night's 22-16 winning start against Leicester Tigers, though all week he was fully confident he would be fit.
But Stevenson's promotion from the Ravens side which hosts Jersey in the British and Irish Cup tonight at Ravenhill has raised fears that the skipper may not have recovered after all.
Either way, the development set alarm bells jangling in supporters' minds ahead of the team announcement.
If it is Williams, Ulster's powerful ball-carrying No 8, who has failed to recover, coach Mark Anscombe will have to rethink. Moving on-song Roger Wilson, who put in a man of the match performance at six against Leicester, to the middle of the back row – his favourite position – would be the obvious answer to the question of who wears eight.
That in turn would leave a vacancy on the blindside and in Ireland's Iain Henderson and Irish-qualified South African, Robbie Diack, the coach has options, too.
But the fact that Henderson could deputise at lock or blindside makes him a vital piece in the jigsaw.