Northern Ireland manager Michael O'Neill believes Oliver Norwood has made a huge mistake in deciding to retire from international football.
The 28-year-old midfielder made the announcement on Monday, saying he wanted to concentrate on his club career with Sheffield United.
"I have no doubt Ollie could have kept playing club and international football for many years," said O'Neill.
"He had the opportunity to leave an incredible legacy and reach 100 caps."
Norwood, who was born in Burnley but qualified to play for Northern Ireland through his grandfather, won 57 caps.
His club Sheffield United are back in the Premier League after a 12-year absence and won their first game of the season against Crystal Palace on Sunday.
"Ollie has been a mainstay of our team for the past seven years. I know this was not an easy decision for Ollie to make, however I think his decision is premature," added O'Neill.
"Ollie will be a loss to our squad, however we have won our four qualifying games to date for Euro 2020 in his absence. The squad will continue to progress, and I believe the players in my squad are more than capable of reaching another major tournament."
Norwood made his full international debut under former Northern Ireland boss Nigel Worthington when he came on as a substitute in a 2-0 friendly defeat by Montenegro in Podgorica in August 2010.
The former Manchester United, Brighton and Fulham man was a regular in O'Neill's midfield when the side qualified for Euro 2016 and played in all four of the team's matches in the finals in France.
He ruled himself out of the squads for the opening four Euro 2020 qualifiers against Estonia and Belarus, from which O'Neill's side claimed maximum points.
"After proudly representing Northern Ireland on 57 occasions, I feel now is the right time to announce my retirement from international football," Norwood said in a statement issued by Sheffield United.
"I've enjoyed the highs of a major tournament - being part of the squad in France at Euro 2016 was the proudest point of my international career.
"I would like to thank the manager, Michael O'Neill, for selecting me on so many occasions to represent my country, and also to the players I've played with through the years. We've had some enjoyable times.
"A huge thank you, too, to the GAWA (Green and White Army) for the tremendous support offered through the years. In my opinion the GAWA really are the best fans in the world and hopefully the squad can deliver more success for them to enjoy."
Norwood, who also played for Northern Ireland's Under-21 and Under-19 teams, failed to score in his 57 appearances for the senior international side.
Sheffield United's promotion to the Premier League last season was a third consecutive promotion for Norwood, who was in the Brighton team that went up in 2017 before helping Fulham win the play-off final in 2018.
The 28-year-old never appeared for either side in the top flight, but, speaking last month, O'Neill had backed him to make the step up this season with the Blades.
Northern Ireland are top of Euro 2020 qualifying Group C with Germany, who have played a game less, in second and Netherlands, who have only played twice, in third.
O'Neill's men have a friendly at home to Luxembourg on 5 September before welcoming Germany to Belfast on 9 September and travelling to play the Netherlands on 10 October.