The Boys in Green succumbed to a 2-1 defeat at Parc Olympique Lyonnais on Sunday, with Griezmann striking twice in quick succession after the re-start to cancel out Robbie Brady's opener.
Their task was made considerably more difficult when Duffy was dismissed for a foul on Griezmann that denied the Atletico Madrid forward a goal-scoring opportunity on the 66th minute.
However, O'Shea believes that Duffy's foul "kept [Ireland] in the game" and said that the Blackburn Rovers centre back was "outstanding".
"Shane had to make that decision [to foul Griezmann]. It kept us in the game," the former Manchester United defender told reporters. "Tonight he was outstanding - he relished the situation.
"Himself and Richard - not only the centre-backs but across the pitch - the effort and quality they showed at times was brilliant to see."
O'Shea had to make do with a place on the bench against France, but was introduced to shore up the backline after Duffy's dismissal, making his 114th appearance for Ireland.
Having turned 35 in April, the Waterford native is approaching the end of his career, but he refused to be drawn on his international future.
"I'm not going to get involved in that now," O'Shea said when asked if he would make himself available for the 2018 World Cup qualifying campaign.
"I'm going to enjoy tonight with a special group of players and a special backroom staff and coaching staff.
"It's very different, especially when we had that moment with the fans in the corner - that's something I'll cherish for a long time."
Ireland kick off their World Cup qualifying campaign away to Serbia on September 5.