The Glasgow Rugby player will join older brother Sean to become the 19th pair of siblings to represent the Scots at full international level in coach Matt Williams' only change from the side which beat Italy at home a fortnight ago.
Lamont said: "Williams is a great player and it is a big responsibility I have got but I will just have to concentrate and do my job and I am confident I can do that.
"I have watched him a lot throughout the championships and I know what he can do but I know what I can do.
"I might be a stone-and-a-half heavier than him but I don't think that will make a difference but perhaps if I clatter him a few times early on then I can take the wind out of Wales' sails.
"I have not played against Williams personally but we do play against most of these Welsh guys week-in, week-out in the Celtic League so it's nothing new."
The 22-year-old played down the significance of appearing with his brother for the first time at full international level.
He said: "We were talking about it and it's great to have him there but it's not something that you think about when you are going to make your debut."
Sean Lamont wished his young brother all the best but admitted he might not be of any use to him once they cross the white line at Murrayfield.
He said: "I have not really got any last-minute words of advice for him apart from telling him to have confidence. He's been thrown in the deep end so he has just got to do it.
"We have had a couple of chats about it as you would but I am still pretty new to this myself, I have only got 10 caps at the moment so I am still adapting.
"I don't think I will be nervous for him, I think I will be concentrating on my own game.
"I have got to get that right before I can worry about anyone else, even him. But I am sure he will cope fine."