THERE is no doubt that selecting the match day starting 15 and 23-man squad for tomorrow night's visit of Cardiff has been the toughest of my time as Glasgow head coach.

Normally, if you have a fully-fit side which has just recorded the best result of the season, a coach does not tend to make any changes.

But the circumstances ahead of the Cardiff game are exceptional, in that we have our Scotland contingent returning.

In previous seasons that would have been the signal for those that had been standing in to make way en masse, but such is the quality and depth we now have in the Glasgow squad that rotation has been kept to an absolute minimum.

Of course, Al Kellock is our captain and given that his involvement with Scotland has been off the bench, he will be returning in the second row to partner Tim Swinson.

That has been tough on Tom Ryder, who was outstanding against Ulster, but will now start as a replacement. Tom will see action tomorrow – there is no doubt about that.

At stand-off we will welcome Duncan Weir back in and look to see him continue to demonstrate the maturity he has been showing in his game in recent weeks, both with Glasgow and for Scotland.

I am also delighted to be bringing in Jon Welsh at loose-head and his return in particular has highlighted the level of competition we have on either side of the front row.

In that respect, I want to make a special mention of the contributions of Ed Kalman and Ofa Fainga'anuku against Ulster last time out.

In particular, Ed has had his season decimated by a back injury.

He then just enjoyed the birth of his first child in the build-up to Ulster, yet he came in and delivered a huge performance.

Ofa did likewise against an Ulster front-row that boasted a 40-cap All Black among their ranks.But I am delighted that Jon Welsh, who has also had a tough time of it with injury, is back in line to start against Cardiff.

In October we went there and gave a dominant scrummaging performance in which Mike Cusack was exceptional, to claim an 18-3 victory that resulted from six penalties.

But I believe tomorrow will be a very different game and that is in no small part to the fact that Cardiff have changed their style of rugby.

It is increasingly being moulded by their outstanding young stand-off Rhys Patchell.

I have no doubt that he is a Welsh Test star in the making and his duel with Duncan at stand-off will be a fascinating sub-plot of tomorrow's game.

But this is our final tie before the break and it is vital that we maintain momentum and continue the six-game winning run we are on.

Although we are currently sitting second in the PRO12, our focus first and foremost must remain on staying in the top four and not letting our attention stray beyond the next game.

We had a fantastic atmosphere at Scotstoun last Friday for the Ulster game. And with a similar level of backing behind us against Cardiff, I am sure we will prove equally formidable opposition.