"When the fixture list comes out in the summer, it's always one of the first that the players look for" he said.
"There's a great rivalry there, it's something which comes historically from fixtures between Neath or Swansea and Llanelli in the old days. That brings with it a real passion from the fans, the fixture usually gets one of the biggest crowds of the season and that creates a special atmosphere. We played down there at Christmas and had the first sell-out at their new ground, and likewise, we've had some memorable games at the Liberty with a sell-out crowd as well. When you've got a big attendance, a passionate crowd and a big rivalry, it's one of those games that you want to be involved in as a player."
With the two region's home venues less than 12 miles apart, Thomas says it's the familiarity and closeness that drives the rivalry.
"We live in such a close proximity in south Wales, Ospreys and Scarlets come into contact with each other all the time, that's the fans working or drinking together, and the boys who are playing against each other" he explained.
"It adds to the rivalry really. You'll find that a lot of the players from the two sides are good friends from the national squad and get on really well, but there is a bit of extra bite in the games because you want to get one over on them to be able to have the bragging rights for the next few months. It's bad enough losing a game whoever the opposition, but losing to someone who you see regularly, who you work with, or socialise with, that can hurt, so no one wants to lose these games."
Despite the changes to the professional game since the arrival of the Ospreys and regional rugby, Thomas says that there is a need for history and tradition in rugby, something which the long-standing rivalry with the Scarlets provides:
"We are only a young organisation really, we haven't been going seven years yet so we haven't really had much opportunity to create our own history or to build tradition. That comes with time, and will happen the longer we go on. These games against the Scarlets are the nearest we've got to tradition at the moment, as they spill over from the pre-regional days, they provide us with a bit of tradition that as Ospreys we can take hold of. As a youngster, pre Ospreys, I was fortunate enough to be able to play in some big Swansea V Llanelli games. I remember going across the Loughor Bridge on the bus to take on what was a very strong Llanelli side at the time as a very young player. They were always wonderful games to play in, and I think the rivalry between Neath and Llanelli was always strong as well. I think the Ospreys Scarlets derby is the one Welsh derby that remains that still has that needle in it."