Trump ran out a 4-1 winner in the match, but struggled for consistency after a century break in the opening frame.
And he told Eurosport that most players would have beaten him in such form.
"It was like he didn’t want to win, I don’t know," Trump said. "He kind of dampened the mood a bit, he just didn’t look interested.
It was hard for me to get up for it, I was a little bit tired, and to be honest I was there for the taking against anyone that showed a bit of fight in them, they probably would have beaten me tonight.
"I don’t know if he was tired or whatever, but he didn’t put up much of a fight out there. No-one in the top 16 should ever be doing that. If he could have got it to 2-2, the way the match was going, I was there for the taking, like I said."
Trump will play Shaun Murphy in the quarter-finals, but after Thursday evening's performance he is just relieved to have the chance to play again.
"My concentration wasn’t really there," he said. "I was making silly mistakes, so I’m just happy to get over the line.
That’s the sort of game, you don’t want to go out there and lose that and be on a negative for the rest of the season.
Friday's quarter-final draw is packed full of star names, but Trump says he didn't even know who he was likely to play before taking to the baize on Thursday.
I don’t look at the draw or anything like that. Just taking it one game a time is what everyone says, but…
"Nowadays I just play the game and see who I’ve got when I come off the table," he added. "I just hope for the best and enjoy myself."
Neil Robertson v Kyren Wilson
Mark Selby v Ronnie O'Sullivan
Anthony McGill/Yan Bingtao v John Higgins
Shaun Murphy v Judd Trump