Luke Humphries produced an outstanding Betfred World Matchplay debut to knock out former winner James Wade on Sunday, as Peter Wright, Rob Cross and Michael Smith progressed in Blackpool.
Humphries gained revenge for March's loss to Wade in the UK Open final with a nerveless display as the former World Youth Champion averaged 101 in a 10-3 defeat of the 2007 champion.
Humphries raced into leads of 2-0 and 6-1 to take control of the contest, with Wade finishing 148 to hit back, but the youngster went on to close out an impressive victory.
"It was a very tough draw," said Humphries. "James played well in the UK Open final but it wasn't about revenge - he didn't play his best darts there.
"I got in front of him early on and punished his mistakes. I felt that there was a lot more to give and I had a few slack darts, but my doubles were good at the right times and I can't be too critical of myself."
Humphries has reached four finals in 2021 in establishing himself inside the top 32, and added: "I've been working hard and I think it's paying off.
"This is just the start, I feel like there are better performances to come. I just seem at home on the big stage and I produce my best darts."
Number two seed Wright's bid to claim a maiden World Matchplay title began in comfortable fashion as the 2017 finalist cruised past Danny Noppert with a 10-2 success.
After Noppert won the opening leg, Wright claimed six in a row - including back-to-back 13-darters and a 105 finish - to pull away from the Dutchman.
Noppert hit back with a 13-darter of his own, but a 121 finish from Wright proved key in ending his hopes as four further legs booked the Scot's last 16 date with Joe Cullen.
"It's a win for me but Danny had lots of darts at doubles and let me off," said Wright, who averaged 99.75. "I played rubbish but every day is different.
"I should be over a ton average, easy, that's how I've come to feel in my game."
Cullen celebrated a 10-8 win over Chris Dobey in emotional fashion following arguably the tie of Sunday's double session.
Cullen landed a ten-darter and an 11-dart leg as he took an early 4-2 lead, before Dobey won three in a row to move ahead and also held a 6-5 advantage.
Cullen, though, showed the form which has earned him two ProTour titles in 2021 so far by moving back ahead at 9-7, taking out a key 97 finish after Dobey missed the bull for a 161 checkout to level.
Double ten kept Dobey in the contest, but Cullen was first to a finish in the next and double eight moved him into the last 16 for a third time in four years.
"It's so nice to get the win," said Cullen. "I've played some great games but I've always been on the wrong end of them so to come out on the right end of them is really pleasing.
"A lot's been going on away from darts for me personally, so to get a win like that, on a stage like that against a good friend like that, it does mean a lot to me.
"I'm really good friends with Chris away from the oche and he was gracious in defeat.
"It was a great game - the crowd make things so much better and that game wouldn't have been as good as it was without them."
2019 runner-up Michael Smith returned to winning ways on the Winter Gardens stage with a 10-7 defeat of Ryan Searle.
Debutant Searle shared the game's opening six legs, but saw Smith take out 136 in a run of four straight legs to pull away from the Somerset thrower.
Finishes of 98 and 96 helped Searle pull back to 8-6, but Smith finished a key 95 on the bull to move to the brink of victory and landed a 13-darter to book his last 16 spot.
"I'm happy with how I battled through," said Smith. "This shows how far I've come - I know it wasn't a great game but I don't think I dropped my head once and I showed grit.
"Over the last three years, that's one big part of my game I've worked on.
"I was really nervous - I've not played on stage in front of fans for a long time and 800 sounds like 10,000!"
Smith will now meet Jose de Sousa, after the Premier League finalist swept aside German number one Gabriel Clemens 10-2.
De Sousa won the opening seven legs without reply, and though Clemens produced a 13-darter as he threatened a fightback, there was no way into the contest as the Portuguese claimed his maiden victory in the event.
"It's the first time I've played here and my first win in the World Matchplay, so I'm more than happy," said De Sousa.
"I expected more from Clemens, he is a great player and I'm sure he can do better than this, but I feel great."
Glen Durrant became the first seeded player to exit this year's World Matchplay, losing 10-6 to debutant Callan Rydz as the two-time semi-finalist's form struggles continued.
Durrant exited the Premier League without a win earlier this year, and found himself 5-0 down to Rydz after missing doubles in each of the first five legs.
Double ten in leg six saw Durrant get off the mark, to the happiness of a supportive Winter Gardens crowd, and he also finished 90, tops and a 13-darter in pulling back to 7-4.
Rydz took out 106 and 92 as he moved towards victory, and the emerging talent from Bedlington regained his nerve after three initial missed match darts to close out the victory on double ten.
"I came here as a fan four years ago and loved it, and it felt amazing to win," said Rydz. "I haven't played in front of fans since the UK Open last year so it's great to see them back.
"I knew I was going to be the favourite but I like Glen and it's terrible to see him struggle. He's out of form, but he knows I had to go out and do a job.
"I didn't play well at all but I've got a day to put it right now, and I want to take my proper game onto that stage."
Rydz will now take on 2019 World Matchplay winner Cross, who overcame a tough test against Ross Smith to progress by a 10-8 scoreline.
Debutant Smith showed no Winter Gardens nerves with legs of 14, 14 and 13 legs as he took an early 3-1 lead, only to see Cross storm back with six legs in a row.
Smith pulled back to 7-6, 8-7 and 9-8, but Cross crucially denied him the chance to level as double 16 saw him close out the win with a 100 average.
"The throw's good at the minute and everything's good," said Cross. "I think I made myself nervous but it's amazing to be back here - the last time I walked out here I won it.
"Everything that I've missed for the last 16 months was here so I'm very grateful.
"Last year I probably had the hardest year I've ever had. I've worked really hard since January and now I'm starting to reap some benefits.
"I'm enjoying it again. Now I feel that I've got a game that I can go out and win with."
Krzysztof Ratajski progressed beyond the first round for a third successive year by defeating Brendan Dolan 10-4, producing the first ton-plus average of the tournament.
Poland's Ratajski was in ruthless mood as he claimed seven of the first nine legs, all being won in between 11 and 15 darts.
Dolan took out 121 as he threatened a mini-fightback, but missed doubles allowed Ratajski to move 9-4 up and double five ensured his spot in the last 16.
"I know Brendan and I know what he can play, so I'm really happy to win," said Ratajski, who now meets Humphries. "The first match is always hard but I was focused and I won.
"It's one of the most important tournaments of the year so a win here is like many wins in other tournaments. I feel good and I know I can play at a high level."
The first round concludes on Monday with the remaining four ties, headlined by two-time champion Michael van Gerwen's meeting with Damon Heta.
2018 champion Gary Anderson plays Stephen Bunting, Daryl Gurney meets Ian White and Nathan Aspinall comes up against Mervyn King.
The action will be broadcast live on Sky Sports in the UK, through the PDC's worldwide broadcast partners including DAZN and RTL7, and on PDCTV for Rest of the World Subscribers.
2021 Betfred World Matchplay
Sunday July 18
4x First Round
Krzysztof Ratajski 10-4 Brendan Dolan
Callan Rydz 10-6 Glen Durrant
Rob Cross 10-8 Ross Smith
Luke Humphries 10-3 James Wade
4x First Round
Joe Cullen 10-8 Chris Dobey
Michael Smith 10-7 Ryan Searle
Peter Wright 10-2 Danny Noppert
Jose de Sousa 10-2 Gabriel Clemens
Monday July 19 (1900 BST)
4x First Round
Daryl Gurney v Ian White
Nathan Aspinall v Mervyn King
Michael van Gerwen v Damon Heta
Gary Anderson v Stephen Bunting
All matches best of 19 legs.
Each game must be won by two clear legs, with up to a maximum of five additional legs being played before the sixth additional leg is sudden-death. For example, should a First Round game (best of 19 legs) reach 12-12, then the 25th leg would be the final and deciding leg.