Grand Slams in 2005 and 2008 will seem a distant memory if Warren Gatland's men slip up against perennial strugglers Scotland at the Millennium Stadium on Saturday.

Hook has branded the game 'must-win' after the 30-17 defeat against England at Twickenham cast doubts over their 2010 Championship credentials.

Victory is paramount if Wales are to stand any chance of lifting the Championship trophy for the third time in six years this season and Hook - who was one of the shining lights in the loss to England - is under no illusions about the importance of bouncing back.

"Make no bones about it, this is must win," said Hook. "Scotland will be determined to come here and do well.

"Up front they are strong but I think their backline is as well with the Evans brothers (Thom and Max) and the Lamont brothers (Rory and Sean) looking sharp.

"They've brought in Dan Parks who is one of the best tactical kickers about and we have to be aware of that."

Full-back Chris Paterson makes his 100th cap for Scotland while Parks' inclusion is one of three personnel changes.

Phil Godman drops out to give Parks the No.10 shirt while Rory Lamont returns to the left wing with brother Sean moving to the centre to replace Max Evans.

Prop Euan Murray - who missed last Sunday's 18-9 defeat to France on religious grounds - returns to the starting XV in place of Moray Low who had a tough time against the French crime.

Wales on the other hand welcome Tom James onto the wing in place of Leigh Halfpenny while Luke Charteris is dropped in favour of Jonathan Thomas.

One sub-plot overshadowing the build-up to the game is a disagreement over whether the stadium should be open or closed. Wales want to close the Millennium Stadium roof but, under Six Nations rules, both teams must agree and the Scots have refused.

Coach Andy Robinson said: "I think it's an advantage to Wales playing with the roof closed, they're used to doing it.

"We are abiding by the rules, we've made the request, let's deal with it."

Scotland have not beaten Wales at the Millennium Stadium since 2002 when they earned a 27-22 win courtesy of two tries from two-time Lions tourist Gordon Bulloch with centurion Paterson is the only survivor from that day.