That's where we're going to leave the blog tonight and what a way to go out, with Reilly Opelka's upset win.

It's semifinal day at both the Brisbane International and United Cup on Saturday and ABC Sport will bring you digital coverage of all the major results.

Enjoy the rest of your evening!

Reilly Opelka spoke to the Nine Network following his win over Novak Djokovic.

The reality is we have nothing to lose coming in against him. He's the greatest player ever so you end up playing more free … you take a lot more risk because it's your only chance.

When asked how he stayed composed as he served for the match, Opelka replied:

I just focused on my spots. If I hit them, it's hard to hit them back. If there is anyone who can, it's him and I was ready for that.

OPELKA WINS!!

A stunning upset, as American Reilly Opelka takes down Novak Djkokovic in straight sets.

Opelka won 7-6 (8/6), 6-3, icing his quarterfinal victory with an ace.

What a performance!

Standing at 6'11", Opelka — who has a protected ranking — produced a superb serving performance against the 24-time major winner.

He hit 16 aces and gave up only one double fault for the match.

Opelka finished with 36 winners to Djokovic's 15, although he did tally 27 unforced errors across the two sets.

It wasn't a case of Djokovic playing badly, instead Opelka — whose career had been struck down by injury — raised his game to another level.

He'll play France's Giovanni Mpetshi Perricard in the semifinals.

For Djokovic, the plan now will be to re-group and focus on the Australian Open, which begins on Sunday week.

Reilly Opelka is in the box seat, leading Novak Djokovic 5-2 in the second set.

Both players won their most recent service games.

Given how well Opelka has served this evening, it's hard to see how Djokovic can fight his way back, given he's down a break in the second set.

It's now 4-1 to Reilly Opelka after he held serve in the fifth game.

The American has fired down 14 aces for the match, landing 81 per cent of his first serves.

Opelka has endured an injury-marred career but he was ranked as high as 17 in the world in 2022.

Do we have an upset on the cards?

Reilly Opelka is producing quality tennis against Novak Djokovic.

He has broken Djokovic in the fourth game of the second set to lead 3-1.

He earlier won the first set in a tie-break (8-6).

Reilly Opelka has seized the advantage against Novak Djokovic, clinching the tie-break 8-6 with an ace down the middle.

The towering American — standing at 6'11" (211cm) — converted on his second set point.

Djokovic looked frustrated at the change of ends but if there is any player who can get themselves out of this position, it's the 24-time major winner.

No surprises here … the first set will be decided by a tie-break.

It's a case of waiting for one of them to blink.

Novak Djokovic and Reilly Opelka haven't even given up a break point so far in the first set.

It's 4-4 … are we heading towards a tie-breaker?

Both Novak Djokovic and Reilly Opelka have walked onto Pat Rafter Arena ahead of their quarterfinal.

The winner of this evening's match will play France's rising star Giovanni Mpetshi Perricard in tomorrow's semifinal.