Scarlets full-back Liam Williams and prop Samson Lee will miss Friday's European Champions Cup trip to Leicester.
But Williams' shoulder injury should heal in time for Toulon's visit on 24 January, two weekends before Wales' Six Nations opener against England.
Lee is also recovering quickly from his neck injury.
But Scarlets hooker Ken Owens (neck) is sidelined while scrum-half Gareth Davies' knee injury is a worry.
Wales international Williams went off during Scarlets' 22-7 Pro12 defeat by Glasgow last weekend.
Wales open their 2015 Six Nations campaign against England on Friday, 6 February.
Williams, capped 18 times, is seen as a serious contender for a place in the team against England.
Former Wales dual-code international Jonathan Davies believes Gatland should pick Williams at full-back ahead of Toulon star Leigh Halfpenny.
"He's playing at the top of his game," said former fly-half Davies, 52.
"Confidence is oozing from him, he just glides past people, he looks comfortable with the ball and he's brave under the high ball."
Williams started at full-back in the historic 12-6 win over South Africa in November 2014, and played in the absence of the injured Halfpenny during the summer tour of South Africa.
Scarlets have a number of other concerns, including a shoulder injury to back-row forward Aaron Shingler, who also left the field against Glasgow.
Club captain and hooker Ken Owens has not played since September.
Owens' Parc y Scarlets hooking colleague Emyr Phillips' Six Nations hopes were ended by a dislocated shoulder.