How six words from Aussie tennis star Alex De Minaur rescued his girlfriend Katie Boulter after she crashed out of Wimbledon

Aussie tennis star Alex De Minaur had six simple words for his girlfriend Katie Boulter following her heartbreaking defeat in the second round at Wimbledon - 'one match doesn't define your career.'

It followed Boulter, 27, losing to compatriot Harriet Dart in dramatic fashion on the Number One Court at the All England Club.

The 32nd seed squandered a number of match points in the third set - with fierce rival Dart breaking down in tears with Boulter leading 6-2 in the final tiebreaker.

Dart, 27, composed herself to remarkably win eight of the final 10 points - and progressed to the third round following an incredible three-hour, 4-6 6-1 7-6 (10-8) victory.

'One match doesn't define my career. That's the first thing he [de Minaur] said to me when I got off the court,' a shattered Boulter told reporters post match.

'He knows what he's talking about. It's not his first rodeo. He's been through it all before, and I'm lucky to have that support.'

Some fans online labelled Dart's on-court conduct as 'unsportsmanlike' - while another suggested it was a case of 'crocodile tears' to desperately swing momentum in her favour.

De Minaur watched the late drama unfold in Boulter’s player’s box just 45 minutes after an impressive showing against Spaniard Jaume Munar.

Earlier, de Minaur cruised into the third round in the men's singles after a comprehensive 6-2 6-2 7-5 win over Munar.

'It's never easy playing in these conditions and closing a match out,' the world No. 9 said.

'I played some great tennis.'

He will next face world No. 212 Frenchman Lucas Pouille after Aussie Thanasi Kokkinakis was injured in their match during the third set and had to withdraw.

If Sydneysider de Minaur continues his impressive form, he could take on No. 2 seed Novak Djokovic in the quarter-finals.