Caldwell hails 'world's best' Boruc

The Poland keeper made several good saves in the first half to keep the visitors at bay but he came into his own in the penalty shoot-out after the game had ended 1-1 after extra-time.

Caldwell said: "In the first half Artur made some great saves and we always knew we were favourites going into the penalties with him in goal. He is without doubt the best goalkeeper in the world and it's great to know that he is behind."

He added: "The number of one-on-ones and penalties he saves says it all, the bigger the game the better he is which is a great asset for a player."

Caldwell, Vennegoor of Hesselink and substitutes Maciej Zurawski and Derek Riordan scored for Celtic with Shunsuke Nakamura hitting the bar.

Mozart netted as did Roman Pavluchenko and Florin Soava but with a save from Egor Titov's effort already under his belt, Boruc saved Spartak's fifth penalty from substitute Maxim Kalinichenko to spark wild scenes of delight inside Celtic Park.

Caldwell, however, saw the other side of Boruc seconds before the half-time whistle when he had to intervene to prevent the Poland international and Lee Naylor taking their spat one step too far.

Boruc had lambasted the former Wolves player for some indecision in defence and the two players had to be separated as they left the field at the interval.

But the Scotland international played the incident down, saying: "It was just two winners wanting to win a football match and the disagreement spilled over.

"It happens at a club like this, maybe more than you think and it was the pressure of the night. Once you get in and sort it out it spurs you on again. It's something that's good and I don't think I would ever knock it out of anyone."