RESULT: Luke Humphries beats Michael van Gerwen 6-5 in final
Van Gerwen secures place in play-offs alongside teenager Littler and world champion Humphries at London's O2 Arena on 23 May
Aspinall (25 pts) and Smith (24 pts) will face each other next week in Sheffield for final play-off spot
Semi-final results: Humphries 6-1 Smith & Van Gerwen 6-1 Littler
Quarter-final results: Van Gerwen 6-3 Price, Littler 6-1 Wright, Humphries 6-1 Cross, Aspinall 3-6 Smith
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Here's how the table looks following tonight's quarter-finals.
The battle for those final two play-off spots is really heating up.
A reminder that fourth will play fifth in Sheffield next Thursday in the final weekly night of the season.
Image source, BBC SportBefore we look ahead to the semi-finals, here is a quick reminder of what happened in the quarters...
Result: Nathan Aspinall 3-6 Michael Smith
There was nothing wrong with Nathan Aspinall's scoring, he hit three 180s and averaged 99.
In comparison, Michael Smith averaged 93.9 with four maximums.
But the The Asp was only three of 14 on the outer ring, that's just 21.4%.
That meant Smith's 40% was enough to see him progress.
Nathan Aspinall 3-6 Michael Smith
How big might this win prove for Michael Smith!?
Nathan Aspinall's finishing has cost him in recent weeks and it does again.
Countless darts at double went begging during the match, including three at double 18 in this one.
Smith capitalised and he moves into the semis, where he will face Luke Humphries.
Nathan Aspinall 3-5 Michael Smith
Laura Turner
Ex-Women's World Championship quarter-finalist on Sky Sports
That is a little opening for Nathan Aspinall but he's got to show perfection from here on in.
Nathan Aspinall 3-5 Michael Smith
Image source, PA MediaGood hold for Nathan Aspinall.
A very steady 13-dart hold to keep this one going a bit longer at the very least.
Nathan Aspinall 2-5 Michael Smith
Laura Turner
Ex-Women's World Championship quarter-finalist on Sky Sports
That is sensational stuff from Michael Smith.
Nathan Aspinall 2-5 Michael Smith
Michael Smith has got himself into a groove now.
After a 180 set-up, he coolly takes out 63 and is now just one leg away from a very important win.
Nathan Aspinall 2-4 Michael Smith
Image source, PA MediaSuperb from Michael Smith!
Nathan Aspinall gave Bully Boy a sniff with a wayward couple of darts, not giving himself a shot at a double when on 78.
That was all Smith needed. Treble 20, treble 20, double eight.
Nathan Aspinall 2-3 Michael Smith
After such an impressive break in the previous leg, Michael Smith loses his advantage with a poor one.
Nathan Aspinall cashes in. Double 10 gets him the immediate break back.
Nathan Aspinall 1-3 Michael Smith
A crucial break of throw for Michael Smith.
He is chasing in the race for the top four and an 11-dart break is just what he needs to try and get past one or both of Nathan Aspinall and Michael van Gerwen.
Double nine seals this leg.
Nathan Aspinall 1-2 Michael Smith
Neither player is looking particularly clinical at the moment.
Michael Smith had the chance to hold but couldn't find the double 19 he needed.
Nathan Aspinall had his opportunity to break but missed a couple of darts at tops.
Eventually, Smith does hit double 19 to hold. He'll take it.
Nathan Aspinall 1-1 Michael Smith
A comfortable hold for Nathan Aspinall.
Another 180 puts him in control and this time he can afford to miss a dart at double 16.
It would have given him a ton-plus checkout but he'll take the 16 out that draws him level.
Nathan Aspinall 0-1 Michael Smith
Rod Studd
Commentator on Sky Sports
Who knows how important that leg might turn out to be in the final count.
Nathan Aspinall 0-1 Michael Smith
Nathan Aspinall starts strong and hits the first 180 of the match - but then misses four darts to break.
A let off for Michael Smith and he takes advantage, just.
He misses tops, then double 10 but hits double five to hold.
Nathan Aspinall v Michael Smith
Anyway, forget walk-on tunes. This is perhaps the most important match of the Premier League season so far.
It could have a massive impact on who makes the top four...
Nathan Aspinall v Michael Smith
It's Nathan Aspinall which can only mean one thing... it's Mr Brightside time!
I've heard it said that it's been massively overplayed over the years but you try telling that to a darts crowd who will happily belt it out three times in a Premier League night when The Asp makes the final.
The fans in Leeds get involved for Shut Up and Dance, Michael Smith's walk-on song, as well but nothing quite matches The Killers classic.
Nathan Aspinall v Michael Smith
Nathan Aspinall talking to Sky Sports: "It is unfortunate that it is Michael [Smith] because we are really good pals.
"I'm going to go up there and do my job and I'm confident I can get the two points and those points will qualify me for the play-offs."
Nathan Aspinall v Michael Smith
Michael Smith talking to Sky Sports: "It is just another game. Next week is the most crucial because it is the last chance you get.
"Tonight is just about having fun. Yes, if I win I get close to Nathan but next week is the most important."
Nathan Aspinall v Michael Smith
Image source, BBC/ GettyOur fourth and final quarter-final tonight is a big one!
Just three points separate third-placed (well, at the start of the evening) Nathan Aspinall and Michael Smith, in fifth, in the table.
A win tonight would put Aspinall in a great position to clinch a top-four berth while anything less for Smith could curtail his chances.
Aspinall has won two nights this year but went out to Luke Littler in a last-leg decider in the quarters last week.
Smith beat Peter Wright in his quarter-final but was blown away by a Littler masterclass in the semis.
It's all to play for...