Northern Ireland head coach Michael O'Neill was left disappointed following his side's defeat to Wales
O'Neill was seen berating fourth official Felix Brych at the final whistle after Saturday's defeat, which was sealed courtesy of Gareth McAuley's unlucky own goal 15 minutes from time, bringing an end to Northern Ireland's Euro 2016 adventure.
Northern Ireland players react at the end of the match
But O'Neill was unhappy at the way officials handled an injury to Wales captain Williams, who picked up a suspected shoulder problem following a nasty collision with teammate Jonny Williams.
The Swansea City ace received extensive treatment following the clash, before appearing to sit down on the pitch in some considerable pain in the closing moments of the game.
Wales players celebrate after the game
And O'Neill was unhappy that he was allowed to stay on the field, adding that it may have hampered his side's attempts to find a leveller.
According to the Daily Mail, he told a press conference after the game: "The (Wales) dugout told Williams to sit down on the pitch and the referee stopped the game. I said he needs to leave the field but the game continued. It’s the first time I’ve ever seen that in my life that a player is allowed to stop play by sitting down on the pitch.
Wales' Ashley Williams and Jonathan Williams sustaining injuries after colliding
"That was disappointing for us that it wasn’t handled better."
The Northern Ireland boss was also unhappy by the amount of injury time added on at the end of the game in Paris, adding: "I felt that the injuries were longer than the four minutes.
"We also had six substitutions in the game. I know my maths is good but I thought we deserved a couple of minutes at the end of the game to possibly force an equaliser."