Joe Schmidt has said Johnny Sexton will be "fine" to face Samoa despite the Ireland fly-half icing his thigh after the win over Russia.
Joey Carbery was withdrawn from Ireland's matchday 23 against Russia after suffering ankle irritation in training on Wednesday.
Andy Farrell has called on Ireland to channel the spirit of England's 2007 World Cup run to turn their Japanese campaign on its head.
Ireland insist Joey Carbery is fully ready to deputise at scrum-half after "numerous occasions" honing the role in training.
Johnny Sexton will captain Ireland for the first time in Thursday's World Cup clash with Russia after recovering from injury