Taulupe Faletau has been ruled out for three to four months after suffering a grade three medial knee ligament injury.
Faletau sustained the injury during Bath’s European Champions Cup match against Toulon last Saturday.
‘It’s obviously a bit of a blow,’ said Bath coach Todd Blackadder. ‘I spoke to him after four big games for Wales about how he was feeling both physically and mentally and he was really good.
‘It was just one of those things. A guy, sort of off the ball, dives sideways through his knee. These things happen.’
Faletau is Wales’ third Lion to be ruled out of the Six Nations. Jonathan Davies is sidelined until May because of a foot injury, while flanker Sam Warburton will miss the whole season after having knee surgery.
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