Ireland fly-half Jonathan Sexton was rated "doubtful" on Monday for their Six Nations clash against Scotland after a Dublin defeat by England on Sunday left them with several injury worries.
Sexton went off after half an hour in what an Ireland team statement Monday labelled a "particularly attritional international match" and was replaced by veteran stand-off Ronan O'Gara, who struggled as England won 12-6 at a rainswept Lansdowne Road.
Irish officials said a scan had confirmed the injury, which they said made Sexton "doubtful" for the game away to Scotland on February 24.
Immediately after the match, Ireland coach Declan Kidney said Simon Zebo would miss the rest of the Six Nations.
This too was confirmed Monday, with the statement saying: "Wing Simon Zebo is definitely ruled out for the remainder of the championship after fracturing his fifth metatarsal in his right foot.
"He underwent surgery on the injury today (Monday) with an expected eight to 10 week recovery period."
Star centre Brian O'Driscoll (right ankle) and lock Donnacha Ryan (back) are both due to see a specialist this week for further review, but neither are ruled out of the Scotland match at present.
Lock Mike McCarthy is doubtful for Murrayfield with a knee injury.
Ireland added full-back Rob Kearney was recovering well after suffering a dead leg, while flanker Sean O'Brien, who came off with a tight hamstring, will be monitored throughout the week.
In addition to their injury problems, Ireland could also find themselves without Cian Healy after the prop forward was cited Monday for stamping on England's Dan Cole.
Healy's case will be before a disciplinary panel in London on Wednesday.
England, the only side to win both their opening two matches, currently top the table while Ireland are one of four sides on two points.