Humphries and Littler have developed an ever-growing rivalry in the sport, with both exchanging titles throughout an intriguing season.
The pair are also still scrapping for this year's world number one spot, which could be decided on Sunday if they meet in the Grand Slam of Darts final.
Littler, 18, could seize the mantle from 'Cool Hand' Humphries if he makes the finale at the Wolverhampton event.
Humphries, though, admits 'The Nuke' has shown an extra consistency which gives him a higher platform.
"I think you just say things in the moment, but I think his ceiling is a lot more consistent than mine," Humphries said.
"I can perform at these levels, but I don't maybe do it as often as he does.
"Maybe that's just a credit to him. He's got such a great throw, and he just does it time after time."
Stressing he wasn't being negative about his own game, Humphries added that Littler has a knack for delivering on the big stage.
"I think he just does it a lot more, like these big ton-plus averages," he said.
"But now I'm starting to feel a little bit comfortable. I can perform at that level as well.
"We're close to each other, but at the moment he's got the edge. It's up to me to get better and try and keep on his tail."
A final showdown is not guaranteed between them, with Humphries still needing to negotiate a semi-final against Gerwyn Price on Sunday afternoon.
But he still welcomed the prospect of taking on Littler for the title later in the day.
"Of course I'd love to meet in the final. I love playing him," Humphries said.
"I get on really well with him and it's always a good prospect playing him in a good final. I really get up for it, and he does as well."