Champions Cup semi-final: Scarlets v Leinster my biggest game - John Barclay

John Barclay captained Scotland for three games in the 2017 Six Nations, including their first win over Wales in 10 years

Scarlets' Champions Cup semi-final against Leinster will be the biggest game he has played for the Welsh region, says back-row John Barclay.

The 31-year-old Scotland captain joined Scarlets from Glasgow in 2013 and will return to his homeland to join Edinburgh for 2018-19.

Scarlets travel to Dublin to face the Champions Cup favourites Leinster at the Aviva Stadium on Saturday.

"It's comfortably the biggest game I've been in at the Scarlets," said Barclay.

"The final of the Pro12 last season was fantastic but this is Europe and we haven't been in the semi-final for 11 years."

Scarlets beat Leinster 27-15 in the Pro12 semi-final at the RDS last season despite having Steff Evans sent off early on in the match.

This season in the Pro14, Leinster and Scarlets finished first and second respectively in Conference B, the Irish side topping the table by five points.

"We are not under any illusions," said Barclay. "We are playing the favourites for the whole competition who form the backbone of the Irish team.

"They are coming off the back of a Grand Slam and are favourites for a reason.

"It's going to be tough and a big challenge but this group of players enjoy these occasions like we showed last year."

'The contact will be huge'

John Barclay has made over 100 appearances for Scarlets since joining from Glasgow

Barclay added that Scarlets will have to be defensively at their best against a Leinster side which scored more points than any team in the Pro14 this season - scoring an average of almost 30 per game.

Leinster also won more try bonus-points than every team except from Conference A winners Glasgow.

"We are away from home in Europe so we are going to have to defend very well," said Barclay.

"They've got a lot of bonus point wins in the league so their attacking prowess is pretty impressive, but defensively we've been good all year.

"We've got a great culture and everybody wants to work hard while we've also got a lot of guys who are good over the ball."

The Scotland international added that discipline will be key if they are to reach the Champions Cup final.

Barclay said: "We will need to be smart so that we don't give too many penalties away. If they get down to the far end and they are holding the ball it's going to lead to points.

"The contact will also be huge, as will other areas like the scrum and lineout.

"All these things will be huge and whoever wins these small battles will likely win the game."