Saracens have been handed a major boost after Liam Williams was declared fit for Saturday's crunch European Champions Cup game against Ospreys.

Williams has not featured competitively since sustaining an injury around his groin and hernia while playing for Wales against Georgia on November 18.

His last club match came on October 28 against London Irish.

But Williams trained with the Saracens first-team on Tuesday and Wednesday, with director of rugby Mark McCall delivering a confident verdict on the 26-year-old's fitness.

"He's available for selection," McCall said.

"He's trained yesterday (Tuesday), he's trained today (Wednesday) and if there are no ill-effects from today's training session, which was the tougher of the two days, then he's got a great chance of being involved in the squad.

"We've taken our time but he looks pretty good. Today and tomorrow he needs to make sure there's not a reaction to today."

Williams would be thrown in at the deep end against his native Ospreys, in what is effectively a knock-out fixture in Pool Two.

Saracens, the defending champions, trail their opponents by two points with two games left and know defeat at the Liberty Stadium would all but end their hopes of progress.

"It's always a calculated gamble to bring someone back who hasn't played for a bit," McCall said.

"But I think you do have the odd exceptional player who is able to do that and is good enough for you to want to put that player in. Liam is probably in that category."

Billy Vunipola and Maro Itoje are both expected to start after each came through a gusty win over Wasps last weekend unscathed.

Vunipola made his first appearance since September following a knee injury, while Itoje was back earlier than expected after breaking his jaw in December.

Saracens are now bidding to keep alive their hopes of a third consecutive European crown and to avoid a first exit before the tournament's quarter-finals since 2011. Their last pool match is at home to Northampton.

"It's the first time for a few years we've been in a fifth pool match where everything is on the line," McCall said.

"It's a new experience for us even to be in that position so early in the competition. It is what it is. If we win we've got a chance of getting to the quarter-finals."

The win over Wasps was Saracens' third on the bounce following a dismal run of seven consecutive defeats at the end of last year. McCall suspects a corner has been turned.

"It hasn't been perfect and it hasn't been without some difficult conversations," McCall said.

"I'm not going to tell you what we discovered but that obviously required us to have, with the staff, coaches and players, harder conversations about where we want to go and how we're going to get there and is what we're doing good enough?

"It wasn't much, but not much is quite a lot sometimes."