The Nick Kyrgios steam train has been derailed by Roberto Bautista Agut at the ATP Cup, leaving Australia up against it to qualify for the final of the inaugural event.

Kyrgios was a shadow of the player who had racked up a 3-0 singles record and decisive doubles win at the teams tournament, going down on Saturday night to the Spanish No.2, 6-1 6-4.

Alex de Minaur must beat Rafael Nadal to push the tie to a deciding doubles match.

The winner will play the Novak Djokovic-led Serbia in Sunday night’s final after they beat Russia 3-0 in the first semi-final.

It was an inauspicious start for Kyrgios who was broken for 0-2 and, when he handed Bautista Agut another after an ill-advised serve volley on a second delivery, the set was as good as over.

The Australian knuckled down to hold at 0-5, ensuring he’d at least be serving first in the second set against the world No.10.

A tighter contest ensued early in the second but another turning point came for Kyrgios on serve at 2-2.

Down a break point, the world No.29 thought he’d brought the game back to deuce with an ace, only to have a let called.

Two serves later, he miscued a forehand long, was broken and destroyed his racquet, a rare behavioural blemish in what had been a week of largely good conduct by the often temperamental 24 year-old.

He saved two match points in the ninth game but the ultra-consistent Bautista Agut served out the rubber.

It leaves a tough ask for de Minaur who is none from two against Nadal and must pull off the biggest win of his career.

If he upsets the world No.1, Kyrgios might yet get a chance for redemption, captain Lleyton Hewitt likely to reprise the Canberran’s doubles combination with de Minaur that saved four match points to beat Great Britain in the quarter-final.

Still, it has been a good Australian Open tune-up for Kyrgios, logging an impressive win against world No.6 Stefanos Tsitsipas on the way.

-AAP