New Haven, CT, USA, 23 August 2018 | AAP

Australian world no.24 Daria Gavrilova battled back from a second-set match point before going down in a tough loss at the Connecticut Open.

In a stern test ahead of next week’s US Open, defending champion Gavrilova fell to 25th-ranked Aryna Sabalenka 6-3 6-7 (6-8) 7-5 in a seesawing second-round clash at the New Haven WTA event on Wednesday.

The ninth-seeded Gavrilova recovered after facing a second-set match point and was 0-4 down in the third before drawing level at 4-all, but dropped serve for a ninth time to ruin her chances of a great comeback win.

.@SabalenkaA takes out defending champion Gavrilova!

Books her spot in the @Connecticutopen quarterfinal 6-3, 6-7(6), 7-5! pic.twitter.com/pBbpfxMMD6

— WTA (@WTA) August 22, 2018

“It was like crazy match for sure,” Sabalenka said. “I’m a little bit in shock that it finished on my side.”

The match swung wildly with Gavrilova’s serve broken nine times and Sabalenka’s seven, as double faults (25 total) and errors (103) mounted.

The ninth-seeded Gavrilova went 5-2 up in the second set but blew two set points before being broken and facing a match point at 6-5 down.

She forced a tiebreaker and closed it out on her fourth set point.

But Gavrilova’s momentum stalled as she quickly fell two breaks behind in the third set.

The relentless Aussie wouldn’t lie down, though, breaking back twice to draw level at 4-all.

The turning point came in the next game when the shrieking Sabalenka saved two break points to halt Gavrilova’s momentum.

With the chance gone begging, the fiery Aussie was one point away from another tiebreaker but Sabalenka lifted once more to land the knockout blow.

“I’m so tired and so happy at one time,” Sabalenka said.

“With every point, I start to be more crazy. I was so angry at myself. And I was just like ‘you have to (win) this because you led 4-0’.”

Ekaterina Makarova backed up her first-round shock win over fourth-seeded Czech Karolina Pliskova by overcoming Magdalena Rybarikova 2-6 6-3 6-3.