Jack Conan is unlikely to play any part in the 2020 Six Nations after Leinster confirmed that the injured Ireland back-row will be out for up to six months following surgery.
Conan played in the World Cup win over Scotland before fracturing his foot in training and flying home.
The Dubliner will also miss the pool stages of the Champions Cup as last year's runners-up Leinster attempt to win a record fifth European crown.
Seán Cronin, who also flew home from Japan with a neck injury, will be further assessed this week but will not be available for Leinster's trip to Italy to play Zebre in the Pro14 on Saturday.
Out-half Ciarán Frawley has made his return to on-field training following an ankle injury and will continue to increase his workload but is similarly unavailable for selection this week.
Ed Byrne returns to training this week following a neck injury and will be continually assessed ahead of Saturday.
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