Ireland boss Joe Schmidt is expected to gamble on taking just two scrum-halves to the Rugby World Cup.
Schmidt is thought to have opted for extra cover at centre in the form of Ulster's Darren Cave, at the expense of Isaac Boss or Kieran Marmion.
Any injury to Conor Murray or Eoin Reddan could see Ireland turning to fly-half Ian Madigan at nine, in a move that carries inherent risk in a highly specialist role.
Kiwi head coach Schmidt will announce his 31-man World Cup squad at a press conference in Dublin on Tuesday lunchtime.
Ireland face England at Twickenham in their final World Cup warm-up match on Saturday, and open their Pool D campaign against Canada in Cardiff on September 19.
Wing Andrew Trimble could miss out in another surprise, with Nathan White and Tadhg Furlong both bolters at prop.
Loosehead Cian Healy will be included despite his continued battles with recovering from neck surgery in May.
Marty Moore's inability to prove his fitness owing to foot trouble should see the Leinster tighthead omitted, however, while veteran centre Gordon D'Arcy should also miss the final cut as expected.