Just a flick off the pads from Mitchell sends Mathews' delivery for four down the leg side.
New Zealand are 10 runs away from almost guaranteeing a semi-final place.
Post update
Stephan Shemilt
BBC Sport chief cricket writer
Chris Silverwood is sat outside the dressing room and looks fed up.
That's a face he pulled when he was England coach.
NZ 157-4
Target 172
No boundaries come from that over, but New Zealand did pick up seven runs, with some aggressive running off that Madushanka over from the Black Caps.
Anyone connected to the New Zealand team will be delighted by this. Sri Lanka, less so.
Post update
Stephan Shemilt
BBC Sport chief cricket writer
I love a partnership like this, Phillips and Mitchell. It's partially due to family connections. This quite often happens in New Zealand.
Post update
While New Zealand have cruised today, captain Kane Williamson fell on just 14.
Video content
Video caption: New Zealand lose third wicket as Williamson is bowled for 14New Zealand lose third wicket as Williamson is bowled for 14
NZ 150-4
Target 172
New Zealand reach 150 with Glenn Phillips scoring a boundary off four runs in the opening ball of his innings. It is perhaps a surprise he did not come into bat before Chapman did.
Just 22 more to go and with Mitchell and Phillips out there, nothing is out of the question!
Post update
James Franklin
Former New Zealand all-rounder on BBC Test Match Special
My sense is when there is a run out like that it's down to the player ball watching.
Post update
Daniel Norcross
BBC Test Match Special commentator
Mitchell ran on the wild yah-hoo, Chapman was just out of his ground.
WICKET
Chapman run out (Samarawickrama) 7 (NZ 145-4) Target 172
A massive mix-up and Chapman is gone!
Chapman goes to smash it, mis-hits that shot and picks out the fielder at gully.
Mitchell ran the quick single, Chapman does not and Mitchell makes it across, with Chapman's short outing coming to an abrupt end.
An easy, simple, a relaxed run out at the non-striker's end for Mathews.
NZ 144-3
Target 172
Ouch, that one looked sore.
Mitchell drove the final ball of the over, it crashes into Madushanka's foot and properly loops right up into the air. It looked like a painful blow to add to Sri Lanka's woe, with 12 runs coming off the over.
A little break while he gets some treatment, but New Zealand need just 28 from here to seal victory.
Post update
Daniel Norcross
BBC Test Match Special commentator
Beautiful lofted shot from Mitchell, 11 from the over so far.
NZ 143-3
Target 172
And now, another four.
This time, Mitchell carved Madushanka over mid-on for a one-bounce four, with this game very much almost over now.
Post update
Daryl Mitchell is into the 30s, with his shots so far including this six.
Post update
Daniel Norcross
BBC Test Match Special commentator
Chapman has done what he's been sent out to do. He carved Madushanka's ball.
He is definitely getting this over and done with.
NZ 136-3
Target 172
That's why Mark Chapman was bumped up the order, crunched for four!
Chapman swatted that one to the rope over the covers, a leap towards 172 and the semi-finals.
NZ 132-3
Target 172
While New Zealand do lose another wicket in the over, the Black Caps still manage six runs from Mathews' second over.
Having been forecast a fair bit of rain today, we've not had any and with 19 overs now gone, this will officially be a match in one over, which New Zealand have all but won, barring a sudden implosion.
Dilshan Madushanka returns to the attack.
Post update
Daniel Norcross
BBC Test Match Special commentator
New Zealand have brought out Chapman with intention to get this over and done with.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
That's unlucky. It just clatters off the stumps. It was there to be hit.
Williamson just lost his shape a bit there.
WICKET
Williamson b Mathews 14 (NZ 130-3) Target 172
Four and out from Williamson!
Having started the over by showing more attacking intent, it backfires for Williamson here as he chops on to his own stumps.
New Zealand still want this over quickly, with the attacking Mark Chapman bumped up the order and coming in next.
Video content
Video caption: New Zealand lose third wicket as Williamson is bowled for 14New Zealand lose third wicket as Williamson is bowled for 14
NZ 126-2
Target 172
New Zealand's rush continues in the over, eight come from it, including that maximum.
Angelo Mathews continues at the other end after an expensive first over.
Live Reporting
Jonty Colman and Ffion Wynne
All times stated are UK
NZ 162-4
Target 172
Just a flick off the pads from Mitchell sends Mathews' delivery for four down the leg side.
New Zealand are 10 runs away from almost guaranteeing a semi-final place.
Post update
Stephan Shemilt
BBC Sport chief cricket writer
Chris Silverwood is sat outside the dressing room and looks fed up.
That's a face he pulled when he was England coach.
NZ 157-4
Target 172
No boundaries come from that over, but New Zealand did pick up seven runs, with some aggressive running off that Madushanka over from the Black Caps.
Anyone connected to the New Zealand team will be delighted by this. Sri Lanka, less so.
Post update
Stephan Shemilt
BBC Sport chief cricket writer
I love a partnership like this, Phillips and Mitchell. It's partially due to family connections. This quite often happens in New Zealand.
Post update
While New Zealand have cruised today, captain Kane Williamson fell on just 14.
Video content
NZ 150-4
Target 172
New Zealand reach 150 with Glenn Phillips scoring a boundary off four runs in the opening ball of his innings. It is perhaps a surprise he did not come into bat before Chapman did.
Just 22 more to go and with Mitchell and Phillips out there, nothing is out of the question!
Post update
James Franklin
Former New Zealand all-rounder on BBC Test Match Special
My sense is when there is a run out like that it's down to the player ball watching.
Post update
Daniel Norcross
BBC Test Match Special commentator
Mitchell ran on the wild yah-hoo, Chapman was just out of his ground.
WICKET
Chapman run out (Samarawickrama) 7 (NZ 145-4) Target 172
A massive mix-up and Chapman is gone!
Chapman goes to smash it, mis-hits that shot and picks out the fielder at gully.
Mitchell ran the quick single, Chapman does not and Mitchell makes it across, with Chapman's short outing coming to an abrupt end.
An easy, simple, a relaxed run out at the non-striker's end for Mathews.
NZ 144-3
Target 172
Ouch, that one looked sore.
Mitchell drove the final ball of the over, it crashes into Madushanka's foot and properly loops right up into the air. It looked like a painful blow to add to Sri Lanka's woe, with 12 runs coming off the over.
A little break while he gets some treatment, but New Zealand need just 28 from here to seal victory.
Post update
Daniel Norcross
BBC Test Match Special commentator
Beautiful lofted shot from Mitchell, 11 from the over so far.
NZ 143-3
Target 172
And now, another four.
This time, Mitchell carved Madushanka over mid-on for a one-bounce four, with this game very much almost over now.
Post update
Daryl Mitchell is into the 30s, with his shots so far including this six.
Post update
Daniel Norcross
BBC Test Match Special commentator
Chapman has done what he's been sent out to do. He carved Madushanka's ball.
He is definitely getting this over and done with.
NZ 136-3
Target 172
That's why Mark Chapman was bumped up the order, crunched for four!
Chapman swatted that one to the rope over the covers, a leap towards 172 and the semi-finals.
NZ 132-3
Target 172
While New Zealand do lose another wicket in the over, the Black Caps still manage six runs from Mathews' second over.
Having been forecast a fair bit of rain today, we've not had any and with 19 overs now gone, this will officially be a match in one over, which New Zealand have all but won, barring a sudden implosion.
Dilshan Madushanka returns to the attack.
Post update
Daniel Norcross
BBC Test Match Special commentator
New Zealand have brought out Chapman with intention to get this over and done with.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
That's unlucky. It just clatters off the stumps. It was there to be hit.
Williamson just lost his shape a bit there.
WICKET
Williamson b Mathews 14 (NZ 130-3) Target 172
Four and out from Williamson!
Having started the over by showing more attacking intent, it backfires for Williamson here as he chops on to his own stumps.
New Zealand still want this over quickly, with the attacking Mark Chapman bumped up the order and coming in next.
Video content
NZ 126-2
Target 172
New Zealand's rush continues in the over, eight come from it, including that maximum.
Angelo Mathews continues at the other end after an expensive first over.