Seamus Coleman has not been selected for the Republic of Ireland squad preparing for the upcoming Nations League fixtures against Kosovo, Israel and Austria.
The former captain was part of the side that competed in international friendlies earlier this month but remains absent from the current 26-strong roster.
The four-match campaign begins with a trip to face Kosovo on 24 September, followed by encounters with Israel on 27 September and Austria on 1 October.
Coleman ended his 17-year tenure at Everton in June of last season after making 433 appearances for the club.
He has been without a club since that departure and is now recovering from a calf injury sustained during Brentford's 1-1 Premier League draw with Sunderland on 5 September.
Several other players were also left out of the squad due to physical limitations, including Collins who suffered an ankle injury, Josh Cullen with a knee issue, Jack Taylor and Mikey Johnston both dealing with knee problems, and Oisin McEntee with an ankle injury.
QPR defender Jimmy Dunne sustained a muscular injury earlier in the month and was consequently excluded from the selection.
In contrast to Coleman's omission, Sheffield United loanee Liam Kitching has received his first call-up to the national team.
Kitching is currently on a season-long loan arrangement from Coventry City and joins uncapped Cardiff City defender Joel Bagan and Hibernian's Owen Elding as new prospects in contention for their debut caps.
The full squad includes goalkeepers Caoimhin Kelleher, Max O'Leary and Gavin Bazanu alongside defenders Dara O'Shea, Jake O'Brien, Liam Scales, John Egan, James Abankwah, Jimmy Dunne, Liam Kitching, Ryan Manning, Joel Bagan and the newly called-up Kitching.
Midfield options comprise Jayson Molumby, Jason Knight, Finn Azaz, Bosun Lawal, Jamie McGrath, Harvey Vale and Conor Coventry while forwards are listed as Troy Parrott, Adam Idah, Chiedozie Ogbene, Tom Cannon, Owen Elding, Jack Moylan and Rocco Vata.