Scotland lock Scott MacLeod will leave Border Reivers at the end of the season to join the Scarlets after agreeing a two-year deal with the Welsh region.
Scott MacLeod is Borders born and bred
MacLeod was left out of the Scotland team to face Ireland on Saturday.
But the 27-year-old said: "I believe I have a lot to offer Scotland at international level.
"And our coach, Frank Hadden, has shown by selecting non-Scotland-based players in the past that you can be selected regardless of where you are playing."
MacLeod previously played for Hawick and has been with the Borders since their creation as one of Scotland's three professional sides in the Celtic League.
He will now play against them for the Llanelli side next season.
"My time at the Borders has been the most enjoyable of my career and I want to thank the coaching staff and fellow players, as well as the Borders public, for being so supportive of both myself and Borders rugby," he said.
"I am a born and bred Hawick lad and this has been a difficult decision but one I needed to make.
"I hope the public continue to get behind the Borders under quality coaches such as Steve Bates, George Graham and Alan Tait.
"Frank Hadden has taken Scottish rugby to a new level and I certainly want to be part of these exciting times."
Hadden insisted that his decision to leave MacLeod out the team for the visit to Lansdowne Road was not influenced by the player's move to Wales.
"Scott has worked hard to regain form and fitness after a prolonged spell out injured," he said.
"He has now won seven caps for Scotland and is among those who have raised the bar of competition at lock.
"It's disappointing to see him leave the Borders. We would have preferred him to stay, but wish him well."