TEENAGER Coco Gauff fell in straight sets to defending champion Aryna Sabalenka to crash out of the Australian Open, to miss out on back-to-back Grand Slam finals.

The American ace, competing in her last major as a teenager, lost her semi-final showdown 7-6(2) 6-4 to the world no.2 in a fiercely-fought contest that lasted 102 minutes.

Gauff, who claimed her maiden Slam with a three set success over Sabalenka to be crowned US Open champion last September, had squeezed into the last four with a gutsy triumph over Marta Kostyuk.

That rare error-filled match against Kostyuk was in stark contrast to her earlier displays at Melbourne Park, when she simply annihilated opponents.

Gauff’s poor performance versus the Ukrainian gave Sabalenka’s confidence a massive boost ahead of their clash.

The Rod Laver Arena crowd were undoubtedly surprised to witness a tense opening set showered with errors, which resulted in an astonishing six breaks of serve.

Yet the Belarusian got her rhythm back to reel off the tie-break for the loss of just two points against the US star who was failing to shine.

Sabalenka turned on the style midway through the second set to book her third Slam final, following in the famous footsteps of Serena Williams by reaching back-to-back Australian Open finals, to oust the out-of-sorts no.4 seed.

Dominant Sabalenka twice broke Gauff to steam into an initial 5-2 lead, but wobbled when serving for the first set in the next game. The American played cautiously as her opponent started to generate unforced errors, and saved a set point with a thunderous serve to level matters at 5-5.

With the bit between her teeth, Gauff broke again to earn a shot at serving out the set. Leading 6-5 30-0, Gauff experienced a nightmare patch. The reigning champion grabbed four points on the bounce to force a tie-break, then reeled off the necessary points with aplomb to seal the set after 57 minutes.

Thankfully the standard vastly improved throughout the second set, much to the delight of the rather passive crowd, with power and precision producing long overdue fireworks. With the result on a knife-edge at 4-4, it was Sabalenka who hit a purple patch when it mattered most.

Gauff was still struggling to find her flow, but battled hard to reach deuce on her serve. A sloppy forehand zoomed into the net to give Sabalenka break point. The teenager was rushed into making her next mistake, her tame backhand attempt gifted the Belarusian the lead.

Although Gauff saved one match point, courtesy of a winner down the line to the backhand, it was Sabalenka’s devastating serve that determined the result.

The no.2 seed thumped down an ace to earn a second match point. She then sent down a tremendous serve out wide, which Gauff failed to handle, to seal the set in 45 minutes.

Avenging her US Open final defeat, Sabalenka left the court with out-of-sorts Gauff now given the chance to reflect on why she narrowly missed out on the opportunity of capturing back-to-back major crowns.

Gauff’s last two outings at the Australian Open produced below-par performances, so she’ll no doubt need to evaluate with coach Brad Gilbert why she seemingly ran out of steam.

Maybe it was due to the fact that she had won her opening 10 matches this year, which included successfully defending her crown at the ABS Classic in Auckland.

Yet the facts explain the loss, with her serving game statistics revealing why she finished second best. A shocking eight double faults and winning just 39% of points on her second serve.

A swift rest and pressing the reset button will soon have Gauff purring again around the courts, to try and continue her formidable form on the WTA Tour where she is vying for more trophies and a shot at becoming the world no.1.