Phil Taylor and Gary Anderson joined Michael Van Gerwen and Raymond Van Barneveld in next week's play-offs at The O2 Arena in London after securing crucial wins in Brighton.
Six-time Premier League champion Taylor showed signs of nerves during his match against Robert Thornton before edging a 7-5 win to book his place in the final four next Thursday night ahead of Peter Wright, who missed out.
Meanwhile, 'The Flying Scotsman' Anderson guaranteed his spot in the play-offs, and a clash against defending champion Van Gerwen, after holding his nerve against fellow Dutchman Van Barneveld.
Taylor, who missed a dart to defeat Wright last week in Newcastle - a result which would have sealed his semi-final spot, rallied from 3-2 down to move 6-3 ahead against the former UK Open champion.
But Scotsman Thornton battled back only to see 16-time World Champion hit double eight in the final leg of the match and qualify in third spot.
'The Power' will next face his old adversary Raymond van Barneveld in the semi-finals.
"Next week's going to be another ding-dong," Taylor told Sky Sports. "It's been the best Premier League I've ever played in.
"I've got a chance to win it. This is the second tournament to the World Championship - that's how much it means to everybody."
The 2011 Premier League champion Anderson was in no mood for any final night hiccups as he cruised past second-placed Van Barneveld 7-4.
Somerset-based Scot Anderson has now won five and drawn two of his last seven matches and heads into next week's showpiece event in dangerous form.
"It was nice to get that one over to be quite honest," he said. "My scoring was great but my doubles were absolutely terrible."
MvG tops table
In the final match of the 15 league nights, Van Gerwen and Wright renewed their new rivalry at the Brighton Centre.
Table topping MvG made sure his darts did the talking on the night following a war of words in the build-up, coming through 7-5 in a thoroughly entertaining tungsten tussle.
Reigning champion van Gerwen ended the league campaign with 11 wins from 16 matches, finishing with an impressive 24 points, and will now face Anderson in the semi-finals.
Meanwhile, colourful Scot Wright, who slipped out of the top four for the first time in his debut season a week ago, had to settle for fifth position.
'Mighty Mike', who averaged 110, said: "I'm very proud of myself (for finishing top) because that's not easy to do."
Adrian Lewis, who already guaranteed sixth spot by defeating Thornton last week, hit six 180's on his way to beating Dave Chisnall 7-4 in a lacklustre contest.
Both players had already been eliminated from play-off contention, but two-time world champion Lewis proved too strong for Chisnall in the end as 'Chizzy' ended his maiden Premier League campaign with his fifth defeat in a row.