Ireland great Paul O'Connell believes Gregor Townsend has created the strongest Scotland team he will have ever faced, either as player or coach.
Ireland play the Scots in Edinburgh on Sunday, with both teams looking for their second wins of the tournament.
Scotland were particularly impressive when beating England at Twickenham in their tournament opener and Ireland forwards coach O'Connell thinks their head coach Townsend has done a superb job.
"There's no doubt Scotland are an excellent side," said O'Connell.
"I think any team that's coached by Gregor Townsend always attacks really well, but going back to his Glasgow days they always have an incredibly physical edge.
"You think sometimes, if a coach is into attack his teams won't have a physical edge, but every single Glasgow team I played back in the day were excellent attacking sides, but they were physical as well.
"And it's the same with this Scotland side now.
"So much of the good attack in the Autumn Nations Cup and the start of the Six Nations has come from Scotland.
"And then they are very, very physical as well.
"It was a fantastic performance by them against England in the first game, an excellent set-piece performance that laid a real solid foundation for them to go on and win.
"I think it's the best Scottish team I've ever gone up against, as a coach or a player.
"They're very well coached, very physical and they've got some real X-factor players as well, (fly-half) Finn Russell to name one and (full-back) Stuart Hogg, just to name another.
"So I think they are in a very, very good place and we're very aware of the challenge."
Ireland began their campaign with defeats to Wales (16-21) and France (13-15) - but are now looking to build on a 48-10 win over Italy.
O'Connell said: "These next two weeks against a resurgent, confident Scottish side, and an English side we've struggled against in recent months and years, it's a real tough challenge now, the last two weeks.
"I think we've taken confidence from some of the things we've done in the last three games; we've probably been unlucky in some regards and we haven't helped ourselves in other regards.
"We've probably given sides a leg-up when we've played them at times - and that's something that we just can't afford to do going forward in the next two weeks.
"You have to be hard to beat, you can't give things away to teams.
"We can't give things away, we can't give teams a leg-up, because this Scottish team will take advantage of that."