The Limerick man insists he will look back on his time on Foyleside with 'great pride' and fondness having played his part in securing European football for the club next season.
The former Waterford winger, who made 35 appearances and added seven assists during his season-long stint at Brandywell, reckons he leaves the club 'a better player' and 'a better person' after a memorable 10 months in Derry.
Fitzgerald's one year contract expired at the end of the season and he later held talks with City boss Ruaidhri Higgins about a potential new deal. However, the player explained his decision to move on was ultimately motivated by a lack of playing time.
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The 22 year-old made over half of his appearances from the substitute's bench and with established League of Ireland stars, Michael Duffy and Patrick McEleney and the talented Will Patching all returning to the club for 2022 and others to follow imminently, Fitzgerald felt his game-time would be limited had he agreed to stay at the club.
"Myself and Ruaidhri stayed in contact and it was a completely mutual decision to leave Derry," he said. "I've always had a great relationship with him but I just thought the next 12 to 18 months of my career is going to be so important for me. So I have to make the right decision for myself and do what's best for me.
"It was tough to have to make the phone call to say I won't be returning because it's a great city, great people and there are a lot of great people involved with the club. It was a difficult decision.
"To be fair I wasn't getting the game-time I was hoping for. We had a good chat and he thanked me and I'm sure our paths will cross again in the future."
Fitzgerald credits Higgins with improving his overall game and believes Derry City are in good hands thanks to the Limavady man's meticulous planning and preparation for games and his 'exciting' vision for the football club.
"Not only do I come away from Derry a better player, I come away from Derry a better man and a better person as well," continued Fitzgerald.
"The city and the people had a big impact on me. And the people involved around the club, to be around them every day was fantastic. For someone who is five or six hours away from home, I was made to feel so welcome.
"I think Ruaidhri helped get the best out of me when he had to and he definitely helped develop my game. To work with that man on the training pitch every day is something I really enjoyed.
"To see a manager who is so prepared for a Friday night game. The players see that and it gives you confidence that if you can execute the plan he has in mind then you will pick up the three points.
"Derry City will be a success," he predicted. "In the next five years they will be a very successful team and will make the city proud. I know from being around it every single day and knowing Ruaidhri's vision, he will execute that vision.
"Knowing and being around that man and having chats with him, he wants the very best for the city and for the football club. Everyone involved and every person in the city should be very excited about the next few years at Derry City."
The lure of playing in the UEFA Europa Conference League next year wasn't enough to entice him to stick around but Fitzgerald says the memories of playing in front of a packed Brandywell and securing fourth place in the league with a final day win over Dundalk will live long in his memory.
"I look back on my time at Derry with great pride. There's great people involved, great coaching staff and I really enjoyed my time there.
"I helped Derry get into Europe which was massive to see the reaction of the fans. At the start of the year to play in front of an empty Brandywell and then at the end playing in front of a packed house in the last game of the season against Sligo is something I'll remember for the rest of my career.
"I was fortunate enough to be there as an opponent five years ago when the Brandywell was re-opened. I always said when I joined that I wanted to play in front of a packed Brandywell, I was lucky enough to do that and I will hold on to that memory for a long time.
"The last game of the season, securing Europe in Dundalk in front of the away fans was something very special and something I will always remember too. Waiting for the Bohs and Sligo result and some of the fans watching the game on their phones and feeling the excitement of getting the win over Dundalk to get that fourth position is something I never experienced before and I might never experience that kind of atmosphere again," he lamented.
"When Pats won the FAI Cup and Derry made Europe it was a fantastic feeling too but it was on the back of my mind that I might have to make a little bit of a selfish decision to try to further my career and take my game to the next level.
"I feel I played my part in Derry getting into Europe. I made a few assists and played plenty of games. Obviously I would have liked to chip in with a few goals .The chance to play in Europe was probably pulling away at me when making my decision but at the end of the day I had to do what was best for me and Ruaidhri totally understood that."
Bohemians boss Keith Long is understood to be an admirer of the winger but Fitzgerald was giving little away.
"I have a few options, yeah. My next decision will be purely based on football reasons. I'm 22 now and I just want to keep developing and get to the next level. Although I have nothing signed just yet I'm very excited to see what the 2022 season holds."
Derry City announced Fitzgerald's departure on social media on Monday morning and Higgins wished him well in the future.
"On behalf of everyone at Derry City, I want to thank Will for his contribution this season and wish him well for the future."