Leo Beenhakker believes Artur Boruc is one of the best five goalkeepers in the world.
The Poland boss feels that his first choice stopper can rightfully claim to be classed in the same bracket as Petr Cech, Gianluigi Buffon, Iker Casillas and Oliver Kahn.
The Celtic star has just helped his club side to a third consecutive SPL title, and Beenhakker admits that he has been forced to work on the keeper's focus after he joined up with his international team-mates with his head 'full of garbage'.
The eccentric coach also believes that Boruc has been distracted by events off the field with speculation continuing to link him with a big-money move to Milan.
However, Beenhakker is confident that the 28-year-old will be mentally stable by the time Euro 2008 gets underway this Saturday.
"Artur's ability is never in question," he said in the Daily Record.
"For me he's right up there with the best and easily takes his place as one of the top five keepers in the world. But to prove that at the Euros his head has to be right.
"He had a difficult start to our training camp because he arrived late, having helped Celtic win the league, and his head was full of all sorts of garbage.
"He's not alone. Part of my job as a national boss is to cleanse the minds of my players and I've done that with Artur.
"Almost all of them come to me with some sort of garbage swimming about in their head.
"It can be positive garbage like the feeling of celebration Artur had for winning the league or it can be negative garbage from a player who has been on the bench all season or one who has just been relegated.
"It's my job to give them clear heads and realise what an opportunity they all have this summer.
"Every player dreams of playing on the big stage like the European Championship and I want them all, not just Artur, to live up to their potential."
The transfer rumours currently surrounding Boruc suggest that he is valued at around £10million and Beenhakker is looking to his keeper to justify that price tag this summer.
"He's enormously talented and has proved that time and time again for Celtic and Poland," said the Dutch coach.
"But how much he would cost in today's transfer market is not my concern.
"All I know is if Artur is focused, if he is feeling confident and is at the top of his game, he's one of the best five keepers in the world.
"He's good enough to challenge with the best and I just hope he shows it. This is a big stage for him, a huge test and I hope he stands up to it."