Wales wing George North could be available for the Six Nations opener against Ireland on 2 February after returning to training with Scarlets.
The 20-year-old was carried off during Scarlets 47-17 defeat by Ulster in the Pro12 at Ravenhill on Friday.
However, a scan showed there was "no serious damage to his neck" and he could be back for Saturday's Heineken Cup trip to Leinster.
"We have to know that he is 100%," warned Scarlets coach Simon Easterby.
"It's important we look after him. We have to see how he goes. We have to be mindful he has had a bit of a wack."
North has scored 11 tries in 26 appearances for Wales.
Centre Jamie Roberts returned from injury for Cardiff Blues in their 17-6 victory at Munster in the Pro12 on Saturday while Leigh Halfpenny recovered from a neck injury to take a place on the bench for the Blues.
However, the defending Six Nations champions have significant injury worries ahead of the annual tournament.
Fly-half Rhys Priestland is out of the 2013 campaign because of a torn Achilles tendon
and is a doubt for the British and Irish Lions tour next summer.
And seven Wales forwards are currently sidelined - prop Aaron Jarvis, hookers Huw Bennett and Ken Owens, locks Alun Wyn Jones, Ian Evans and Luke Charteris as well as flanker Dan Lydiate.