Jonathan Jurejko
BBC Sport at Melbourne Park

Osaka just stands motionless at the baseline after Kvitova blows her off court to break. Looking up, I think, at the big screen, puffing her cheeks out.

Second serve from Naomi Osaka - pummeled for a forehand winner by Petra Kvitova!

Good return from Kvitova, leaping off the floor - and Osaka nets from down low!

Another break point for Kvitova.

Image source, Getty Images

An ace and a "come on!" get Osaka in front...

...and that's a better shot from Kvitova on the forehand, and she darts forward to finish off the rally.

Back to deuce we go.

Oh, and Osaka's backhand helps her slice her way out of trouble!

Deuce.

Kvitova's forehand has temporarily gone walkabout, as she sends a nasty shank over the baseline.

It's working alright on that one, though, a winner going whizzing on to the tramlines for 30-30.

Shot! Down the line goes Kvitova, beating Osaka's outstretched dive, and she's got herself a break point.

A lovely sliced drop shot brings up 30-0 for Kvitova but she pushes her next backhand over the baseline.

A wayward forehand follows and Kvitova is under pressure again. Osaka then tries a curling forehand around the net but misses and Kvitova holds when the 21-year-old slumps a return into the net.

Important hold.

James Stevenson: As expected, a close first set. But not a close tiebreak. Osaka zoned in for that tiebreak. Didn’t look like missing.

Image source, Reuters

Jonathan Jurejko
BBC Sport at Melbourne Park

Not great news for Kvitova. Osaka has won her past 59 matches after taking the first set... Incredible record.

Russell Fuller
BBC tennis correspondent at Melbourne Park

After an incredibly tight first set, she has won the tie-break. She's a set away from coming to Melbourne just after her 21st birthday and adding an Australian Open title.

The first set goes Naomi Osaka's way!

Image source, Reuters

Flat-footed from Kvitova, and a netted backhand gives Osaka four set points.

Forward comes Kvitova - and she's passed by Osaka's forehand!

Change of ends, and Kvitova clonks a first serve down the T.

Ace from Osaka. Kvitova thinks she's heard a net cord, but there's no bleep.

And another lovely cross-court swipe from Osaka, off a Kvitova mis-hit, extends her lead.

Shot! Osaka moves quickly across to pick up the Kvitova wide serve, and times the backside off a winner.

Long goes the Osaka backhand, and Kvitova is on the board.

Jonathan Jurejko
BBC Sport at Melbourne Park

"Ayyyaaahhhhh!" A throat-hurting scream from Kvitova pierces the calm Melbourne air, showing her relief at digging deep to take this set into a tie-break.

Image source, EPA

A deep return from Naomi Osaka, and Petra Kvitova shanks it out of play.

Naomi Osaka will serve first in the tie-break.

Second serve from Kvitova, and it's hit long by Osaka!

A chance for Kvitova to hold - and hold she does with a cross-court winner!

Hello, tie-break.

Kim Clijsters
Four-time Grand Slam champion on BBC Radio 5 live sports extra

I love how both players started with their emotions composed but when the important moments arrive, they are not afraid to show it.