Williams, 34, said: "They're an explosive unit who are well used to playing with each other. I've played against them all many times and it's always difficult. Scotland have picked a tough team so it promises to be a physical game. We'll have to match that.
"They will be hurting from losing on the first week, just like us. So we will all be looking to prove a point."
Wales have won five of the last six meetings between the teams and Scotland have only won once in 13 years in Cardiff. Williams said: "I'm sure Scotland will still be thinking about last year when we really clicked and put them to the sword in front of their own fans.
"I've been in that situation and all you want to do is prove a point the next time you play that team. That will be in the back of their minds and they won't want that to happen again."
Williams will become the third most capped Welsh international tomorrow when he makes his 93rd Test appearance, behind Colin Charvis (94) and Gareth Thomas (100).
He said: "These milestones are things to look back on when you finish playing. When you get to my stage, every game is a bonus and you go out and enjoy it."
And Rob Howley insists today's Six Nations clash with Scotland is a must-win game for Wales. Warren Gatland's men return to Cardiff on the back of hefty defeats to Australia and England last weekend. Andt attack coach Howley has vowed Wales must avoid a hat-trick of losses at the Millennium Stadium.
Howley said: "We want to get back to winning ways as winning and losing can become a habit. There will be pressure on Scotland as they lost at home last weekend while we were away.
"But we have lost the last two games against Australia and England. We are coming home to the Millennium Stadium where we have the greatest supporters in world sport.
"There is expectation from them but we need to have the confidence and self-belief to win. We need to get back to winning ways."
British Lions prop Gethin Jenkins missed the 30-17 defeat at Twickenham but has handed the hosts a boost after passing a late fitness test on a calf strain. Wales forwards coach Robin McBryde said: "Gethin is fit and will take his place on the bench.
"It's a big boost for us. He's a world-class player from the start and we hope he will have the same effect off the bench."