Ramos stepped up to make it 2-1 from the spot, before Luka Modric added a third late in the game. Koeman told Barca TV: "Every decision goes against us. In five games there have been none in our favour.
Barcelona manager, Ronald Koeman, has criticized the referees for not awarding his side a late penalty, as they lost 2-1 to Real Madrid on Saturday. Ferland Mendy appeared to pull Martin Braithwaite down in the last 10 minutes.
Messi headed in his 30th league goal of the season, as Barca lost 2-1 in their final home fixture of the year. The result saw their title hopes end mathematically.
A group of furious Barcelona fans surrounded manager, Ronald Koeman's car, as he drove away from the Nou Camp after their 2-1 defeat to Real Madrid on Sunday.
"That's what happens when you do 1v1 with the iceman Victor Lindelof," he added. Meanwhile, the World Cup-winning star appears to be enjoying his times at Old Trafford since his return from injury.