Jamie Roberts on Six Nations 2014: Dropping Mike Phillips for Rhys Webb was a massive call but Warren Gatland has got so many of those right over the years

If the coach feels a player is ready to step into the XV we all respect that immediately

With his aggressive and high-tempo style Rhys Webb has earned his starting place in the Wales team against France tonight (Getty Images)

As a coach, Warren Gatland has never been afraid to make the big calls. That's what makes him stand out and, of course, again this week he's made some big calls.

The decision to drop Mike Phillips to the bench against France tonight is the stand-out one and I know Mike will be bitterly disappointed with that but it's one he'll fully respect.

First and foremost, Mike is a passionate Welshman who wears his heart on his sleeve every single time he pulls on that red shirt, and he always gives absolutely everything.

I've known Mike for a few years now but have obviously got to know him even better these past few months since his arrival at Racing Métro. He's a great guy, he's so, so passionate and he brings a lot of energy on to the pitch. And I'm sure he'll do that again if and when he comes off the bench tonight.

But only one person can wear the Wales No 9 shirt and Warren's obviously decided that's Rhys Webb. A lot of people might not know him but he's a very impressive player. He's aggressive and he likes to play at a high tempo, which certainly suits the type of game we play as a team.

If Warren feels a player is ready to step into the starting XV then we all respect that immediately. He's made those calls over the years and those calls have been proven right. I for one have no doubts about Rhys and what he can bring as a rugby player, having seen him in training.

Another big talking point is the big man, George North, moving alongside me at outside centre. Wales centres appear to have been dropping like flies, with Scott Williams having had to undergo surgery in the wake of the Ireland game and Jonathan Davies just not quite fit to return.

George will have absolutely no qualms about playing the role. He slotted in there for most of the Ireland game when Scott came off injured. George is a hell of a player, so mature for his age.

Making the move from wing to centre is difficult – just the slight nuances in the different way you play when everything unfolds so quickly on a rugby field. But then there are certain similarities. Defensively, for example, the difference isn't that great and that's an area, as everyone knows, that George is particularly strong in.

Plus, the way the modern game is now at international level we're always switching around positions in a match and he's well versed in coming off the wing into the centre. I know there's been some talk of George's long-term future being at centre rather than wing but you never really know. I played my first two games for Wales at full-back and wing and then I started at 12 and, aside from the occasional game at 13, I've never changed.

For all we know, George could have an absolute blinder of a game and he could go on to become No 13 for Wales for the foreseeable future. You just never know how these things work out. Hopefully he'll put on a good show tonight. We've got a fairly formidable midfield partnership up against us in Mathieu Bastareaud and Wesley Fofana. I've played against both of them recently in France and that's a good thing. You sort of get the chance to run the rule over them a bit and so you're not in for any nasty surprises next time around. It means you're basically not blind to how they play. Fofana is such a talented guy. He's quick and agile, and he can cut the line incredibly quickly if given half a chance. Bastareaud is one of those hugely physical guys and a big ball carrier.

He's one of those players who in defence you simply can't afford to get half a shoulder on. That's asking for trouble. You have to check yourself and make sure you tackle him properly, but it's a balancing act. As well as being a battering ram, he's also a great decoy runner so there's that balance of ensuring you don't commit yourself to that decoy run and leave your team-mates hanging.

It's a pairing that in so many games can put France on the front foot, and George and I have a massive defensive task on our hands. But if you want to be playing in the higher echelons of world rugby, these are the guys you want to test yourself against.

I've spent the last week in Paris and, while I was rested for the game last weekend, there's been no shortage of the usual banter with the French guys. It's all light-hearted stuff, although that will dissipate the moment we get on the field even against our Racing Métro team-mates.

Of those guys, I don't really have to say much about Dimitri Szarzewski. Everyone knows what he can do – he's so experienced and combative. Another club team-mate, Wenceslas Lauret, comes into the side and he's a great player. He's very aggressive over the ball, in fact he reminds me of a Gallic Sam Warburton if such a thing is possible!

They're both very similar players in the sense that they're amazing physical specimens and great athletes. But it's more than that. When Wenceslas is on the ball he's just very hard to budge. Similarly Warby. It's going to be a hell of a challenge for Dan Lydiate, another of my club team-mates, coming up against him.

Looking back at the Ireland game, there's obviously not a lot to take heart from. The one positive I guess was getting to play against Brian O'Driscoll one last time before his retirement.

I would desperately have liked to have had the result go the other way but to be on the field with a player I have learned so much for in one more game and to spend time with him afterwards was actually very special.

You don't need me to tell you that the game in Dublin didn't go to plan. The boys and I were hugely disappointed but there are times in life when you have to doff your cap to a side and we have to do that to Ireland in this instance. Tactically, they were very astute, in fact every facet of their game they got just right.

But just because of the nature of that defeat, it hasn't diminished our belief that we can be Six Nations champions. We've come unstuck against Ireland before and gone on to win the championship, just as we did last year.

With one defeat in two games, it means that tonight's game is massive. It doesn't matter that it's France and what's gone before. In many ways, that's immaterial. What matters is that we have to win this game to keep alive our Championship defence and we fully believe we can do that and win the Six Nations come next month.

We'll approach it with the same intensity, as always. The crowd at the Millennium Stadium will be integral to that, as always. I can't begin to explain what that roar does to you as a player, the way it lifts you, the belief it gives you in that red jersey. They'll believe in us as much as we do in ourselves. That's priceless.