The Romanian stopper was dropped to the substitutes' bench for Manchester City's cup defeat to Wigan Athletic in 2013 after conceding just a single goal in five ties en route to the final, with club number one Joe Hart instead being handed the gloves for the big occasion.
Pantilimon cites that snub as the worst moment in his career, and admits that he has taken care to brace himself in case something similar happens with Watford, with Heurelho Gomes currently in consistent form in the Premier League campaign.
The 29-year-old told the Sun: "[Being dropped] was the biggest disappointment of my career – but that’s in the past and I'm just looking forward now.
"Would I expect to play in the final if we make it? That's a tough question and I can't answer it because it would be down to the manager. He has not promised me anything. He doesn't need to speak too much with me because he knows that, if he gives me a chance, I will give my best and that is the most important thing for me.
"I don't expect to play every round. That's down to the manager and I am just a player doing his job, but it's no secret that the FA Cup is special for me. It's the only competition in England where I don't have a winner's medal in my collection and I hope to have one in future."
Pantilimon only joined Quique Sanchez Flores's side in January after a year and a half spent largely as number one at struggling Sunderland.
Since his arrival at Vicarage Road the goalkeeper has featured in just two FA Cup ties, but kept a clean sheet in both as Watford saw off Championship sides Nottingham Forest and Leeds United with consecutive 1-0 victories.
He will be hoping to be allowed to continue his good cup form as the Hornets travel to the winner of the replay between Arsenal and Hull City in the quarter-finals.
Watford are impressing in their first season back in the Premier League, and currently occupy ninth place in the top flight.