Willis, the World No.772 who came through six rounds of qualifying and the first-round proper, was beaten 6-0, 6-3, 6-4 by the third seed in round two.
"It's like a fairytale. I had a plan and believed, rightly or wrongly, I could win. It was amazing, I wasn't really that nervous -- it was just awesome," Willis was quoted as saying by the BBC on Wednesday.
Willis was in danger of suffering a humiliating defeat when he lost the first seven games, but he gathered himself sufficiently to test Federer.
The Englishman, 25, admitted he was capable of playing better and did not deserve to lose the first set 6-0.
"I thought I played OK. I was in games, I just didn't get on the board. He makes you play. He's class, put me under the cosh and came out firing," he said.
"I did enjoy myself even though I was getting duffed up. I loved every bit of it, though not the duffing bit. I loved getting stuck in, fighting hard. The plan was to get him moving, hit to his backhand but he's not the best player of all time for no reason."
"He's just ridiculous. The big points he played ridiculously well. It wasn't like he was flashy. We all know he can be flashy, but he was just rock solid," the World No.23 added.