The East Preston manager had a number of proven Ryman League players ready to sign if his side had stepped up into the South Divison next season.
But, having been denied the promotion to Step 4, those players are unwilling to step down to the County League.
With them on board, Di Paola believes EP could have made a serious challenge on the top three next season.
Instead, he now has the task of keeping his title-winning side together.
He said: “I am really disappointed and gutted about the whole thing, really. It was to be expected and it is not like it came out of the blue, but it is still a massive disappointment for everyone.
“I feel a little bit let down, but it isn’t anyone’s fault, it is just a collective thing and it’s a bit of a sucker punch.
“Everyone at the club is frustrated about it, though, not just me.
“If all the players want to stay, I will probably end up staying at EP. It’s just very frustrating as I had about five players that would have come in and allowed us to challenge up at the top.
“I was pretty confident that we could have been up in the top three with a really strong side with these guys coming in from Ryman League clubs.
“But, obviously, they are not going to come down and play in the County League, so it’s all very frustrating.”
On his future at the club, Di Paola is waiting to hear back from a number of his players this week, but admits he is likely to stay at The Lashmar next season.
He said: “I had a chat with EP at the weekend and I have had a lot of different offers from other clubs, but nothing too exciting.”