Melbourne VIC, Australia, 14 December 2016 | Matt Trollope

Chris O’Connell held firm in a tense final set to upset No.2 seed Sam Groth at the Australian Open Play-off.

The 22-year-old Sydneysider won 7-5 3-6 7-5 4-6 8-6 to advance to the semifinals, where he will meet Omar Jasika, a straight-sets winner over Gavin Van Peperzeel.

“It feels amazing. I’m in the semifinals and really looking to push forward and keep going,” O’Connell said.

“I seemed to return really well today, I was seeing it really well. And then I was backing it up with my service games.”

With Groth’s exit, not one of the tournament’s top-four seeds remain; earlier on Wednesday, No.1 seed Andrew Whittington and fourth seed Marc Polmans were eliminated, while No.3 seed Marinko Matosevic was shown the door on Monday by Jasika.

Jasika on Wednesday reached the last four with a 6-4 6-0 6-2 win over Queensland’s Van Peperzeel.

> view the Australian Open Play-off men’s draw

The victory over Groth continues O’Connell’s breakout season, in which he has won five ITF Futures titles and improved his ranking by almost 400 places to a career-high No.240.

“One of the biggest things is I’ve been injury free. I haven’t had one injury all year,” O’Connell said when asked to explain the factors behind his rise.

“I decided this year just to play a lot of matches. I think I’ve played over 80 matches this year and I’ve predominantly been in Europe – I was there for about seven months just playing week-in and week-out on the clay so I’ve got a lot match fitness and experience.”

O’Connell nabbed the first set with an athletic backhand smash before Groth – a former world No.53 – got the match back on level terms in the second set.

The players split the third and fourth sets before O’Connell looked to have the match well and truly sealed when he surged to a 4-1 lead in the fifth.

That’s when Groth began to make a charge, landing a barrage of powerful first serves and then breaking O’Connell to love, part of a three-game run that saw him level the set at 4-4.

“When I got broken, I just had to re-set and go again,” O’Connell said.

Games then went on serve – O’Connell held in the next game with a magnificent reflexed forehand winner off a powerful Groth return – until the 14th game.

There, Groth sent two forehands well long and then faced match point when O’Connell produced a flowing backhand passing shot winner down the line.

Groth dumped a backhand volley into the net to give O’Connell the win.

“I feel really good; my legs feel great actually,” the New South Welshman said.

“I’m really looking forward to that next match and if I happen to get through that, I’d love an opportunity to get a wildcard into the Australian Open. It would be awesome.”

For more information, visit the Australian Open Play-off homepage.