Blues flanker Martyn Williams may have to turn down his Royal Wedding invitation and play in the Magners League on 29 April instead.
His side take on Newport Gwent Dragons in a vital rearranged fixture, but he has been asked to attend Prince William and Kate Middleton's wedding.
"It's a huge honour to be invited to the wedding - my wife has bought her hat," said Williams.
"But I still don't know if I'm allowed to go yet," he added.
I'm just waiting to see. I've got to discuss it with my coach."
Williams, 35, capped 98 times for Wales, has signed a new one-year contract with Cardiff Blues but has confirmed he and his wife Sam are among those on the exclusive wedding guest list of Welsh Rugby Union patron Prince William and his bride-to-be.
"I've been fortunate to meet Prince William a few times over the years but I was as shocked as anybody else when I got the invite," added Williams.
"It's the chance of a lifetime really so if I do get the chance to go I look forward to it."
Blues coach Dai Young would have to give Williams permission to miss the game in Newport.
With younger flanker Sam Warburton, 22, injured, Williams' services may be needed as they push to win at least five of their last six matches to make the Magners League play-offs.
Warburton, who limped off with a knee injury in the first half of Wales' 28-9 defeat to France in the Stade de France, is likely to be out of action for a few weeks. The Blues are also without injured wing Tom James, hooker Rhys Thomas and prop Taufa'ao Felise.
"These are massive games for us - everyone knows the value Martyn Williams brings to the squad both on and off the field," said Young.
