The 37-year-old, who joined Hibs as a free agent this summer following his departure from Queens Park Rangers, made the shock announcement just days before the start of the Nations League campaign, having been among the substitutes for the 2022 World Cup play-off semi-final defeat by Ukraine last week.
The veteran shot-stopper amassed 47 caps in nearly 20 years but his last appearance came during last summer’s Euro 2020 group stages, with Hearts No.1 Craig Gordon currently first pick for Scotland.
Addressing Marshall’s bombshell before the squad flew to Dublin ahead of the Nations League meeting with the Republic of Ireland, Clarke spoke of the unexpected nature of the former Celtic and Cardiff City ‘keeper’s decision.
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"It was a little bit of a surprise, certainly the timing, in the middle of the camp,” Clarke said.
"I had a good chat with David and his mind was made up.
"We shook hands, I thanked him for everything he had done for the national team and wished him well for the rest of his club career."
Marshall said that part of his decision was based on giving younger ‘keepers Zander Clark and Liam Kelly more of an opportunity.
Meanwhile, Hibs have broken a significant season-ticket sales barrier ahead of the Easter Road squad returning for pre-season.
The Capital club confirmed on Friday that more than 10,000 season tickets have been sold for the 2022/23 campaign despite the disappointment of last season.
A statement from the club read: “We would like to thank everyone who has joined the journey so far and purchased their Hibernian FC Season Ticket for the upcoming 2022/23 campaign.
"Over 10,000 Hibs fans have secured their seat for next season and will be there to support Lee Johnson in his first season in charge of the club.
"The new season kicks off in under one months time, so if you have not already done so, there is still time to sign up and join the journey.”
The club has frozen ticket prices ‘to thank everyone for all their support during a difficult financial climate’.