‘I worked a lot on my serve. You can’t even imagine.’

“I’m just super happy right now that everything is working.”

Sabalenka and Shelby had clashed twice previously, both last year, with the Belarusian edging each — the most recent a three-set, 2hr 35min epic on hard courts in Cincinnati.

“She’s such a great player, always tough matches against her,” said fifth seed Sabalenka.

“I expected a great level from her. That’s why I said to myself to stay focused from the beginning to the end and probably that’s why I was able to win this one in two sets.”

There was little between the pair again in a 54-minute opening set on Thursday with only a pivotal eighth game separating them.

It went to five deuces on Shelby’s serve before a rasping crosscourt forehand and a scream of “Come on!” from Sabalenka brought up a third break point.

She converted for a 5-3 lead and served out the set to love.

Sabalenka kept up the pressure on Shelby’s serve at the start of the second set, breaking for a 2-1 lead.

The Belarusian was now on a roll, peppering Shelby with an avalanche of winners off both wings — at one point hitting six in a row in her tally of 32 for the match.

“I didn’t really try to go for all those winners,” admitted Sabalenka who will take some stopping in this form.

“I was just picking the target and I was, like, okay, I’ll go there. That’s it.”

Her power surge enabled her to break twice more, ending the contest in style by ripping a backhand crosscourt pass on her first match point.

She is aiming to get past the Last 16 in the Australian Open for the first time and will next play the 26th seed from Belgium Elise Mertens who beat American Lauren Davis 6-4, 6-3.