Rossington's 67* gives Northants win
Middlesex post 132-7 (20 overs)
Bailey top scores with 46 for visitors
Notts beat Essex in first quarter-final
T20 Blast Finals Day on 20 August
Middlesex 78-3 (11.3 overs) v Northants
And Paul Stirling, perhaps acknowledging everything we've just said, has holed out trying to move things forward.
The big opener clears his front leg, launches the ball to long on, where the floppy-hatted Graeme White wheels around to take a smart catch diving forward.
Paul Stirling and George Bailey are still just happily nudging and nurdling here, finding the occasional boundary just to keep the scoreboard ticking over with some sort of pace. But, I agree with James, I'm not sure these two are scoring quite quickly enough.
Azharullah's latest over goes for 10, as both players move past 30.
James Taylor
Ex-England batsman on BBC Radio 5 live sports extra
Image source, Getty ImagesQuote MessageI'd say Middlesex are quite a long way behind where they'd want to be. But they've got wickets in hand so it's not all gloom and doom, and they have a world-class player in George Bailey at the crease too.
Seekkuge Prasanna continues from the other end and has a little more joy than Graeme White, seeing just six come off his latest over.
This partnership is now worth 54 - George Bailey is on 26, Paul Stirling 28.
George Bailey decides he's had enough of a look now though, clobbering two fours in a row from Graeme White's second over to move the away side to 59-2. All very steady from Middlesex.
Seekkuge Prasanna is thrown the ball and, like Graeme White before him, also sends down a very solid set.
Just four runs from that over, all singles, as this game just cruises through a bit of a lull. Middlesex happy to have a look for a couple of overs, Northants happy to let them do just that.
Slow bowler Graeme White is into the attack now, as captain Alex Wakely decides to take the pace off the ball for the first time this evening.
And it's a decent introduction too, limiting the damage to just three runs.
Middlesex 41-2 (6 overs) v Northants
Image source, Getty ImagesPaul Stirling (20 not out) and George Bailey (12 not out) have done a decent job of building a wee partnership here, worth 25 runs now.
Paul Stirling thumps the final ball of the powerplay - bowled by Azharullah - for six to cow corner.
Image source, Getty ImagesHaving limped to two from his first nine balls, Aussie George Bailey biffs Steven Crook for successive fours.
WASP says Middlesex are on course to make 162 - how competitive will that be on this pitch?
Very good stuff from Richard Gleeson, his second over going for just a single. Barring the first two balls of the previous over, Northants have been as solid as a rock so far.
Unlike last night, when it was all about the slower bowling of Samit Patel, Imran Tahir and Steven Mullaney, pace is doing the job for the hosts so far at Wantage Road.
Middlesex 24-2 (3 overs) v Northants
That's a bit more like it from the men in pink, as a no-ball - which went for four - from the first delivery presents Paul Stirling with a free hit, and he duly pulls to cow corner for six.
Rory Kleinveldt recovers to limit the final five deliveries to just two runs, but at least Middlesex are up and moving.
Image source, Getty ImagesA solid set of six from Richard Gleeson, whose first over goes for seven runs. How big a role will opener Paul Stirling need to play now?
Australia batsman George Bailey joins him in the middle.
Middlesex 10-2 (1.5 overs) v Northants
After a streaky four down to third man, Nick Gubbins is sent packing from the very next ball and it's the same drill as the first wicket to fall.
Richard Gleeson finds a little extra pace, and left-hander Gubbins can only play onto his own stumps.
A good start just got even gooder for Northants.
The new man in for Middlesex is Nick Gubbins, who gets off the mark with a dashed single into the offside.
The visitors are 3-1 after the first over of the powerplay.
Middlesex 1-1 (0.3 overs) v Northants
And the Middlesex skipper has gone without scoring!
Rory Kleinveldt, the big South African seamer, finds the inside edge of Dawid Malan's bat and the ball clatters into middle stump.
A massive start for the hosts.
Paul Stirling and Dawid Malan are opening for Middlesex, Rory Kleinveldt has the ball in hand for Northants.
Let's get this T20 Blast last-eight match started.
As the players emerge onto the field, now seems as good a time as any to remind you that you can also listen to live radio commentary of tonight's match by using either the audio icon or 'Live Coverage' tab at the top of this page.
Notts beat Essex by 39 runs
Nottinghamshire became the first side to book their spot at Finals Day, beating Essex by 39 runs last night.
Samit Patel was the hero, returning figures of 4-20, while Chris Read took a couple of high-catching catches behind the stumps.
"Maybe this is our year," Read told BBC Radio Nottingham. "We go to Finals Day full of confidence and hopefully pick up some silverware."
Visiting captain Dawid Malan has won the toss and elected to bat first. The two teams are as follows...
Northants: Levi, Rossington, Cobb, Duckett, Wakely (capt), Crook, Prasanna, Kleinveldt, White, Gleeson, Azharullah.
Middlesex: Stirling, Malan (capt), Gubbins, Bailey, Simpson, Franklin, Higgins, Roland-Jones, Rayner, Sowter, Podmore.
One T20 Blast quarter-final down, three to go.
Part two takes place tonight at Wantage Road, where Northants take on Middlesex in beautiful weather and in front of a rowdy crowd in the East Midlands.
The start is just 10 minutes away, so without further ado I should probably bring you news of the teams and toss...