Only Gary Anderson in 2011 and Glenn Durrant in 2020 have managed the feat so far, but both Littler and Humphries have given plenty of indication that either could add to that list this week.
A few eyebrows were raised when Littler was given one of the eight places this season, but the teenager has more than proved the doubters wrong - finishing the league element of the campaign at the top of the pile after winning four out of the 16 night events.
After a slow start, his first win was delivered in Belfast on Night 9, which was followed by victory in Manchester a week later. Further wins in Liverpool and Aberdeen on Nights 13 and 14 - as well as consistent performances on the nights he didn't win - saw him finish with 40 points at the top of the table.
In second was Humphries, who also succeeded in winning four nights overall, winning three events in a row between Nights 6 and 8 in Brighton, Nottingham and Dublin. By the time his final victory came in Leeds on Night 15, he had already done enough to qualify in the top four.
Michael van Gerwen took the third qualifying spot, winning three of the first four events - Night 2 in Berlin, Night 3 in Glasgow and Night 4 in Newcastle. He also won Night 11 in Birmingham, but it has been an up and down season overall for the Dutchman, who exited in the first round in eight out of the other 12 events.
The final semi-final place was taken by Michael Smith, who beat old friend Nathan Aspinall in the quarter-final of the last event - Night 16 in Sheffield - to progress to the final four.
Smith went on to win Night 16, his second victory of the Premier League season after coming out on top in Night 1 in Cardiff in February. The two victories bookended an otherwise lukewarm season for last year's World Darts Championship winner.
"To qualify and end the season with a win, it feels great,” Smith told the PDC in Sheffield.
"I was literally drained after beating Nathan. I was really emotional because he’s one of my best friends, but I had a job to do tonight.
"I know I won the first week, but to sign off with another one, I’m going into The O2 with a little bit of confidence."
And so to Thursday’s semi-finals, where Littler faces off with Smith and Humphries plays Van Gerwen in a best-of-19 format. The winners will progress to the best-of-21 final to play for a cash prize of £275,000 and the honour of being crowned the 2024 Premier League champion.
Semi-final 1: Littler (1) v Smith (4)
Despite having had a hot-and-cold 2024 overall, Smith has quite often been hot when he's played Littler.
The pair have played each other seven times in total, all in this year's Premier League, and Smith has won five of the seven matches.
Perhaps one thing in Littler's favour is the fact that on the occasions he has beaten Smith, he has done so ruthlessly - winning 6-2 in Exeter and 6-1 in Aberdeen.
If Smith finds his rhythm then Littler could be in trouble, but if Littler is quick out the blocks then he may take a big step towards winning the big prize at the end of the night.
Smith told the PDC: "I know I’ve got a good record against Luke, but it doesn’t matter now.
"This is a different atmosphere, and it feels like a different tournament almost. You have to bring your best game, and hopefully I can bring some good form into next week."
Semi-final 2: Humphries (2) v Van Gerwen (3)
Humphries and Van Gerwen have also played each other seven times in 2024, and surprisingly it's been even more one-sided than the other head-to-head. Humphries has come out on top in all but one showdown; a 6-5 loss in the final of Night 3 in Glasgow.
Thereafter, Humphries has had the number of the legendary Dutchman this year, beating him twice on the European Tour and four times in the Premier League, on one occasion in Europe beating him 8-1.
Humphries is also the reigning World Darts Championship champion, having beaten Littler in the final in January, and is widely considered to be the best player in the world.
However, Van Gerwen is a seven-time Premier League champion which makes him the most successful in the tournament's history - one better than second-place Phil Taylor in the overall winners' standings.
Besides Van Gerwen and Taylor, only one other player, Gary Anderson (2), has won the Premier League more than once, which gives an indication of the was the Dutchman has dominated the competition as well as the sport in recent times.
Everything points to it being a closely fought content in London, despite how much success Humphries has had over Van Gerwen this year so far.