Hatters striker remains hopeful he can add to his caps for Ireland
The 29-year-old made his debut for his country last season against New Zealand, while scored his first goal in the 3-1 friendly win over Bulgaria earlier this term.
He was hoping to be part of the squad that travelled to Slovakia for their Euro 2020 play-off match due to take place recently, only to see the game postponed due to the cornonavirus pandemic.
With the finals also now taking place 12 months later to allow the current season to hopefully reach a conclusion in the summer, Collins said: “I was due to be in Slovakia playing in the qualifying game but it wasn’t to be for bigger reasons.
“People do think that it is all over for the Euros, but it’s just been put to the back burner.
"The games have been changed now to early June so that is another reason for me to try and stay on top of my fitness and look after myself.
“Because if those games go ahead then you have to be ready because they’re massive games for the country and we want to be in the Euros in 2021.
“So we need to make sure we’re ready to go when the games do come around.”
If Collins is called up again, it will under a new regime, with U21 boss Stephen Kenny taking over from Mick McCarthy at the weekend.
Kenny was set to replace McCarthy, 61, after Euro 2020 but the postponement of the play-offs and the tournament itself until 2021 led the FAI to bring their plan forward.
McCarthy said: "It's disappointing that I can't finish it off, but I think we had a really good campaign.
It's been brilliant - I've loved being back. I've thoroughly enjoyed it and it's been an absolute pleasure and an honour to do the job again.
"And I think I'm leaving Stephen with a healthy balance to be quite honest. I support the decision that has been made."
Meanwhile, Kenny added: "Mick has had a tremendous career as captain of Ireland and as manager of Ireland on two occasions.
"It's unfortunate for him with the cancellation of the matches but he leaves a legacy and is revered in Ireland.
"There have also been contributions over the last few years from Robbie Keane, Terry Connor and all of the staff."
"It's a good day for me but we're not in celebratory mode.
"My thoughts are with the frontline workers - the doctors, nurses, paramedics and everyone.
"The self-sacrifices are heroic and we really support them."