Warren Gatland will be awaiting news on this injury over the coming days.
With just over a week left until the Lions squad is announced for the 2017 Tour to New Zealand, players across Ireland, England, Wales and Scotland will be hoping they have done enough to get a spot on the plane.
When it comes to the captaincy, there are a number of players who are in contention.
These include Sam Warburton, Alun Wyn Jones, Rory Best, Conor Murray, Dylan Hartley and Owen Farrell.
However, there has been a level of agreement in most quarters that Warburton will resume the captaincy after leading the Lions in Australia in 2013.
The 28-year-old is undoubtedly a leader, and since he relinquished the Welsh captaincy to Jones and moved back to the six position, Warburton has flourished.
This, in addition to the fact that Gatland trusts him, makes it all the more likely that he will lead the Lions in what will be a grueling Test series against the All Blacks.
However, Warburton’s candidacy now remains in doubt.
The back-row forward was substituted after 37 minutes with a knee injury in the Cardiff Blues’ 24-24 draw with Ulster at Kingspan Stadium.
Blues head coach, Danny Wilson, spoke to the BBC after the game and revealed that Warburton will go for a scan.
“He had a bang to his knee. We’ll get a scan and have him assessed as soon as possible,” Wilson said.
The seriousness of the injury won’t be known until he has been assessed but you can be sure Gatland will be one of the first to know of the 28-year-old’s prognosis.