Ireland captain James Ryan is a doubt for Saturday's Test match against Japan due to an adductor issue.
The Leinster second row, leading the side for games against Japan and the USA in the absence of rested skipper Johnny Sexton, was expected to be in the frame for a call-up to the Lions when their captain Alun Wyn Jones was ruled out with a dislocated shoulder on Saturday.
However, the adductor injury and the short timeframe, with the Lions landing in South Africa this morning, mean that the 24-year-old remains in Ireland.
"James Ryan has an adductor issue and will be monitored across the week to determine his availability for the Japan game," the union said.
The team for the Aviva Stadium clash (1pm, live on RTÉ1 and RTÉ Player) will be named at lunchtime on Thursday.
