Wales and Cardiff Blues flanker Sam Warburton faces approximately six weeks on the sidelines after suffering a knee injury.
The 28-year-old picked up a medial ligament strain during Cardiff Blues' 24-24 draw against Ulster in Belfast last week.
Warburton, who has been heavily tipped to captain the British and Irish Lions in their upcoming tour to New Zealand, crossed for a try during the 23rd minute of the Blues' 24-24 Guinness PRO12 draw at the Kingspan Stadium but left the game before half-time due to injury.
Blues head coach Danny Wilson confirmed Warburton's absence but says he does not envisage any problems with regard to the Welshman's availability for this summer's Lions tour.
"Sam has a low grade medial strain which will put him out for approximately six weeks, which won't interfere with the Lions," said Wilson.
"You see players who get back quickly if they follow religiously the protocol and they get a bit of luck.
"And I am sure that will be the case with Sam in terms of him following the protocol, and then we will see, all being well, how quickly he can come back. 'Low grade' was the important bit of news," he added.
Warburton gained his first international cap in 2009 before going on to skipper the Lions in Australia four years ago and has emerged as a strong contender to captain the Lions, with Wales team-mate Alun Wyn Jones a doubt for the tour.
Jones, who captained Wales during the Six Nations, suffered a shoulder injury against France and will not be reassessed until early May.
Lions head coach Warren Gatland is due to announce his squad on April 19, ahead of their opening fixture against a Provinical Union team on Saturday 3 June.
Watch the announcement live on Sky Sports News HQ from midday.
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