New Zealander Mike Delany will not be able to play for Clermont in their European Cup semi-final against Munster this weekend as he is ineligible, competition organisers European Rugby Cup (ERC) said on Tuesday.
The fly-half, who won his sole All Blacks cap in 2009, was signed by Clermont as a medical joker earlier this month to replace injured youngster Julien Farnoux.
But a spokesman for the Dublin-based ERC said the French Top 14 leaders had not registered the 30-year-old Delany in time.
"A team which qualifies for the knock-out stages has until March 21 to register three extra players. Clermont didn't register any," he told AFP.
"Lately there has been a request from Clermont to register Mike Delany and the club was told he could not play."
The Vulcans announced Delany's signing on March 19 but he only arrived at the club on April 9.
Even if Clermont beat the Irish province on Saturday, Delany, who signed a permanent two-year deal with the French side on Monday, would not be eligible for May's final either.
Clermont coach Vern Cotter had been hoping Delany, who has been first choice fly-half since joining the club, would play against Munster as regular Australian No.10 Brock James is struggling to recover from a thigh injury.
Delany's absence would leave veteran former France half-back David Skrela as Clermont's only fly-half option.