Ulster could find themselves squeezed between a rule change on one side and a former Ravenhill favourite on the other in their quest to replace Gloucester-bound keyman John Afoa with a tight-head of similar standing.
The IRFU ruling body's revised rules regarding overseas players mean that ex-Ulster but now-Munster tight-head, South African BJ Botha, is already ensconced as the one permitted foreigner in that position across the four provinces.
As things stand, Ulster cannot recruit a non-Irish No3 to fill the massive void left by Afoa when the New Zealander makes his end of season £500,000 a year move to the English Aviva Premiership on a four-year contract.
A special case for dispensation would have to be made to the IRFU, the Ulster worry being any future injury to present Irish international back-up in the position, Declan Fitzpatrick.
Ulster's Kiwi coach Mark Anscombe acknowledged the difficulty, ahead of tomorrow's Heineken Cup clash with Treviso in Italy, saying: "We are working with the Irish Rugby Union to ascertain what we are allowed to do as obviously there are restrictions with foreigners in certain positions. If, in every province, there was an overseas tight-head prop it wouldn't help the development of Irish props."
Up until now Fitzpatrick has been Ulster's tight-head understudy, covering Botha until his departure at the end of 2010-11 and Afoa since his arrival.
"Deccie Fitzpatrick, you know, in the last six months has really solidified his game. You saw it at international level," Anscombe said.
"When he comes off the bench for John we are very fortunate that we don't drop our standards.
"Deccie has proven that off the bench with Ireland in New Zealand and in November.
"He is growing. If we can keep him on the pitch and he stays injury-free – and that has happened this year – we are going to see the best of him."
But tight-head is a punishing position which takes a physical toll, requiring rock-solid, ever-present performers in anchoring the scrum.
But with Botha at Munster, Humphreys knows he will have to be even more persuasive if he is to convince the IRFU to let Ulster enlist another overseas tight-head.
Humphreys is working on the development of a case the IRFU will not be able to refuse. That will not be easy.
Yarde's contract expires at the end of the season and while the Exiles want to retain the 21-year-old who is beginning to make a name for himself in international rugby, they insist any deal must offer value.
Interim executive chairman David Fitzgerald has revealed "substantial funds" are available following a takeover by a consortium of London-based Irish businessmen.
But Fitzgerald insists the club will operate a sustainable business and avoid the type of extravagant spending spree that has seen French club Toulon assemble a squad of international stars.