But the former St Mirren midfielder aims to use those feelings to kick-start his career after returning to Scotland.
Mallan felt ready to make an impact in the Sky Bet Championship after making more than 100 first-team appearances for Saints before his move last summer.
But he had to wait until Boxing Day for his debut and only played nine games in total.
It was a difficult season for the club with manager Paul Heckingbottom leaving for Leeds in February before his successor, Jose Morais, departed after they were relegated.
Mallan secured a move to Hibs and the 22-year-old is set to be thrown into action as they host NSI Runavik of the Faroe Islands in their Europa League opener at Easter Road on Thursday.
“The main factor was playing,” Mallan said. “I only played nine games or so for Barnsley and coming from playing week in, week out for St Mirren to hardly playing at all was a tough, tough ask.
“I found it mentally tough because I felt I could have played and obviously I got left out of a lot of squads.
“It was a massive learning curve. The first three or four months were hard. I spoke to the club psychologist. He was always about the club.
“I would say he helped me a lot because he kept me always thinking positive and to take my chance when it came.
“It’s something I had never experienced, being left out a lot, and I think it has helped me to not want that feeling again. It gives you that extra bit of hunger to keep showing what you can do. “I have come here to play and stamp my authority on the team.”
Mallan, who hit 29 goals for St Mirren, added: “I knew the jump was massive going from the Scottish Championship to the English Championship. It’s not until you get here that you think: ‘Wait a minute, I can play’. “I felt I could have played a lot sooner than I did. It’s the manager’s choice but I did feel I could have played a lot more.
“Now I’m at a key stage in my career where I just need to play games and I felt this was the right opportunity for me to do that.”
Mallan’s final game for St Mirren was at a packed Easter Road as his team secured their Championship status before Hibs lifted the trophy. And he is relishing the thought of playing there on a regular basis.
“I played against Hibs quite a lot and the way they played, a lot of attacking football, and the size of the club as well, it was an opportunity I couldn’t knock back,” he said.
“When the opportunity came about, I wanted to be here so much. I spoke to John (McGinn) as well and he has loved his time here. To see how much he has kicked on, it’s good to see someone who came through at St Mirren with me do so well.
“He said one of the main reasons he has done well is this club and how they have pushed him on. That was also a big enticement.”