Barkley came under fire once again for another below-par display while Lukaku failed to register a single shot at goal.
Everton’s 3-1 defeat attracted a lot of criticism – especially from former pros including Jamie Carragher who questioned Lukaku’s displays in the big games this season.
But Koeman launched a fierce defence of his star forward and says it was wrong to single out the club’s top goalscorer for the defeat.
Koeman said: “What I don’t like is too much individually about the performances of the players because it is a team, every individual is part of the team and the team was not good enough.
“I said not too much individually but maybe some players didn’t perform at the level what maybe they showed in the last few games. Maybe, yes.
“Romelu, it was difficult. I spoke to Romelu, he was not really sharp, he was a little bit tired.
“(But) he’s the top-scorer of the league. Why now about the Liverpool game (do) we need to criticise Rom? He’s a great striker, he’s working hard. It’s a human boy, it’s not always a 10, that’s football and if you don’t play football, maybe you don’t understand it.”
Koeman was also unhappy with the attention that surrounded Barkley and says he is working hard on different aspects of his game.
Koeman added: “Ross played in a little different position than he played in the last few weeks. Of course, he lost several balls in the midfield, instead of playing a little bit faster and no dribbling with the ball.
“He needs to improve in that, but not to take out one or two (players for criticism) and that was the problem last Saturday, that’s not fair.
“It’s easy to give your opinion in front of the television without any responsibility. I’m happy, I see a lot of progress in the club, in the team, it’s a whole season, it’s not one game.”