Saracens also say that Williams, who has been sidelined since October with an ankle injury, could rejoin Welsh region Scarlets earlier than expected.

Saracens need to reduce their costs in order to comply with the Premiership's £7m salary cap for this season.

"I think he might be fit for the Six Nations, but I don't think he will be fit for us before that," McCall said.

The English Premiership champions Saracens were deducted 35 points and fined £5.36m in November for breaking rules over three seasons.

Saracens will not be contesting their punishment, while Premiership Rugby has announced a "comprehensive review" of its salary cap regulations.

Williams will join Scarlets next season after three campaigns in England. When asked if the deal that will see Williams returning to Wales could be brought forward from this summer, McCall added: "It is possible.

"It is not ideal," he added. "Liam hasn't played a game for us this season. That's not his fault.

"It was Liam's decision that he was going to go back to the Scarlets and to Wales and that was a family decision.

"We understood that completely and he doesn't regret coming here and we don't regret bringing him to Saracens, he has been brilliant."

The news that Williams is winning his battle to to be fit for the start of the Six Nations will be a big boost to Wayne Pivac as he prepares for his first major tournament as Wales coach.

Williams suffered an ankle injury in training before the World Cup semi-final against South Africa in Japan.

However, McCall warned that Williams is unlikely to get any game time for his club before Wales' first match on 1 February against Italy in Cardiff.

"I don't think he will be fit for us before the Six Nations, so it is not ideal, he hasn't played a game for us this season, but that isn't his fault, he got injured before the World Cup semi-final," McCall added.

"I think he will be ready for the start of the Six Nations."