The Englishman converted eight from nine shots at double to deny the Polish number one his first tournament win of the season.
Aspinall, who is a former UK Open champion, progressed to his fourth Players Championship final of the year and delivered the goods to claim the £12,000 prize.
The 31-year-old held his throw comfortably in the opening leg, before seizing total control of the match with back-to-back 11 and 12 darters.
Aspinall then pinned deadly 70 and 64 combinations to stretch his insatiable lead to 7-1. While Ratajski did claim successive legs to make the score look a tad more reasonable, it was the Stockport star who sealed the win with a two-dart 58 checkout.
"I've not played fantastically today, but I've dug deep and I've produced big legs and finishes that matter," said Aspinall, celebrating his seventh PDC title.
"It feels good that I've won a tournament without playing my A-game at any stage.
"My Grandad has come today. He was there for my UK Open win and I've won a Pro Tour now, so I won't be able to get rid of him, he'll want to keep coming back!
"It's been a torrid 12 months for me. I fell down the rankings, and I'm still in pain [from his injury] now, but I'm absolutely buzzing.
"I'm enjoying my darts again. When it's so close to being taken away from you, it gives you so much motivation, and I want it so much."
Players Championship 22 Results
Ryan Searle 6-2 Luke Humphries
Nathan Aspinall 6-4 Stephen Bunting
Danny Noppert 6-4 Michael Smith
Krzysztof Ratajski 6-5 Dimitri Van den Bergh
Nathan Aspinall 7-6 Ryan Searle
Krzysztof Ratajski 7-5 Danny Noppert
Nathan Aspinall 8-3 Krzysztof Ratajski