Michael van Gerwen suffered a shock quarter-final exit to world number 52 Scott Williams, who will face Luke Humphries in Tuesday's semi-final after Cool Hand Luke comfortably downed Dave Chisnall 5-1.
Catch up on the action from earlier in the day here.
Relive all the action from the final two quarter-finals at Alexandra Palace on Monday night below:
Michael van Gerwen (2) 3-5 Scott Williams (52)
Van Gerwen missed a handful of arrows in the first leg to grab the first break and saw Williams hold his own leg.
In the second leg, Van Gerwen opened with his first 180 of the match and missed the double 16 from 132 to keep his own leg, allowing Williams to break from 50 to take a 2-0 lead in legs.
Again in the third leg, Van Gerwen could not finish and Williams took the first set in straight legs - the first set dropped by MVG in the tournament.
In the first leg of the second set, Van Gerwen also missed darts on the double but still managed to keep his own leg. Van Gerwen missed his 12th dart on a double of the match and Williams was able to keep his own second leg.
From 144, Van Gerwen was allowed to dock for a nine-darter, but arrow number seven was not perfect. He did, however, take his own third leg in 11 throws.
The men traded 180s and from 81 Van Gerwen took the fourth leg and the set, making it 1-1.
Costly misses
Throwing out 100, Williams managed to keep his own first leg of the third set.
Van Gerwen scored superbly and was 2-2 in legs after a 121 finish. The fifth and deciding leg was started by Williams, who threw his sixth 180 of the match, missed four set arrows and saw the set go to Van Gerwen.
In the first leg of the fourth set, Van Gerwen ran into a break. The Englishman cashed in on his break and took the set from Van Gerwen.
In the third leg, Van Gerwen missed four arrows to keep his leg, allowing Williams to take another set in straight legs, levelling the match at 2-2.
Williams won his fifth leg in a row after grabbing a break in the second leg of the fifth set to race to a 2-0 lead in legs.
Williams ran into no trouble in his own third leg and took another set in straight legs, celebrating in front of the Dutchman at times, much to the world number two's chagrin.
Van Gerwen hits back
Van Gerwen grabbed the first two legs of the sixth set, helped by a break from 100 (treble 20, double 20) and managed to take the third set in straight legs, without missing a dart on the double, making it 3-3 in sets.
Scoring left much to be desired on both sides at the start of the seventh set and Williams took advantage of poor putting away by Van Gerwen. The Englishman took the fourth leg, which Van Gerwen had started, and eventually takes out tops in the next leg to win the set 3-1 in legs.
It's 4-3 to Williams in sets - is Van Gerwen in danger of going out?
Williams misses three chances to take out 40 so MVG returns but misses three of his own.
Williams then can't find double 2 allowing Van Gerwen to pin double 1 for the hold.
The Englishman then races to a double 8 finish to level things up 1-1 in legs. He kicks off the next with the 21st 180 of the match, followed by a strong second showing to really apply pressure for the break.
With 58 to finish, Williams hits the tops to give himself a leg away from victory and the darts in his hand. Massive break!
MVG comes back with a 180 but then a poor 1. Williams charges back with a maximum of his own.
No treble for MVG, opening the door for Williams. He leaves 44 to put the favourite out.
Williams takes out double 16 to send the three-time world champion tumbling out of the tournament. A quarter-final shocker at Ally Pally!
Luke Humphries (3) 5-1 Dave Chisnall (11)
Chisnall was broken by Humphries in the second and fourth leg and lost the first set 3-1, after notching a break himself in the third leg.
Humphries recorded an average of 103.61 in the first set, whereas Chisnall stuck at 88.61.
The first four legs of the second set all went with the arrows.
The highlight was Humphries' 164 finish in the fourth leg. Both men started the fifth leg with 180 and Chisnall managed to keep his own leg to win the second set, making it 1-1.
In the third leg of the third set, Chisnall missed two darts on the double for a break and saw Humphries take a 2-1 in legs lead.
A leg later, Chisnall himself was broken and Humphries won the set: 2-1 to Cool Hand.
Humphries steals
Chisnall threw out the first two legs of the fourth set in 11 and 12 throws to take a 2-0 lead in legs.
Humphries grabbed a break back in the third leg and managed to hold his own fourth leg to force a fifth.
Chisnall only had one arrow on the double to keep his own leg and set - which he missed - allowing Humphries to eventually break via double 1. It goes 3-1 to Humphries.
While scoring went well for both men, they missed numerous doubles in the fourth leg of the fifth set. Humphries missed five set darts but was allowed to start the fifth leg himself to win the set.
From 121, a decent tap-out was given to Chisnall, who fell behind 4-1 in sets.
Humphries thundered through by getting directly ahead by a break in the first leg of the sixth set. In his own second leg, he got to match point.
From 117, the first match dart went straight in and Humphries recorded a convincing win.
Humphries will play Scott Williams in the semi-final on Tuesday.
