John Barclay hopes playing at a "really special" Rugby World Cup in Japan can help banish memories of missing out on the tournament four years ago.

The back-row was omitted by Vern Cotter for the 2015 edition after finding himself largely frozen out of the Scotland squad.

And the 32-year-old says it remains the biggest regret of his career.

"My biggest disappointment in 15 years of rugby was to not get picked for that squad," Barclay told BBC Scotland.

"It's something that motivated me not just this year, but motivated me to get back involved with Scotland and really push for that. I'd love to go to another World Cup."

'I've still got a lot to prove'

Barclay made his Scotland debut against the All Blacks in the 2007 World Cup one day before his 21st birthday. He was a mainstay of the side four years later for the tournament in New Zealand and has amassed 71 caps.

"I went to my first [World Cup] when I was just a kid," he said.

"I didn't really understand the position I was in and didn't play a lot. The second one, I went as a regular starter and it'll be a different dynamic this time.

"I've still got a lot to prove to myself and to the team and I would just love to go to a World Cup in Japan with Scotland. To be part of this group would be really special."

Barclay joined Edinburgh last season but had to wait 10 months before making his debut in March after suffering a horrendous Achilles injury in his final appearance for former club Scarlets.

He says the goal of being part of Gregor Townsend's squad for Japan kept his spirits high during the painstaking recovery process.

"It's something I thought a lot about when I was injured, when I was struggling to hit milestones in my recovery," said Barclay.

"Mentally I feel pretty fresh, I don't feel drained from a season which can be the case sometimes.

"My body feels really good. There's a lot of training to do but for me it was great to get a few games in, have a bit of a break and then begin this road to the World Cup."

'I don't know how you can pick this squad'

Townsend named a training squad of 44 which will be whittled down to 31 once the head coach has a closer look at his options during a training camp in Portugal and summer Tests against France and Georgia.

Barclay believes, if he is selected, it will be the strongest Scotland World Cup squad he will have been part of.

"I genuinely believe, and I've been playing with Scotland a long time, this is a team that has some depth and some quality," he said.

"I sat on the team bus and said to some of the guys, 'I don't know how you can pick this squad'.

"In years gone by you could easily pick a 31, but this time there are going to be some guys who probably deserve to be on the plane missing out because you can only take 31. That can only be a good thing for us as a squad."