Blues manager Koeman is livid after Ireland counterpart O’Neill decided McCarthy was fit to face Wales in last Friday’s World Cup qualifier, only for the player to be withdrawn after feeling a hamstring problem in the warm-up.
The 26-year-old is now expected to be out for a lengthy spell.
And with Everton playing away to Liverpool and Manchester United in the space of four days in the next week, Koeman could barely contain his anger at the decision of O’Neill and McCarthy.
He said: “It was a final decision against the [judgement of the] medical staff of Ireland and also against the medical staff of Everton.
“And there are two people responsible for that.
“One is the player by himself. Finally, if he says, ‘Yes. I’m fit’, okay, but even the player needs protection from the manager and, once again, they didn’t give that protection to the player.”
O’Neill and Koeman have been at loggerheads for a while over the treatment of McCarthy.
O’Neill and Chris Coleman react to Seamus Coleman injury
And for the Everton boss — who also looks like being without midfielder Morgan Schneiderlin for the double-header at Anfield and Old Trafford — this was clearly the final straw.
Koeman has had an unfortunate international break, with central defender Ramiro Funes Mori being assessed after going off with a knee injury in Argentina’s defeat in Bolivia and, of course, the terrible injury suffered by full-back Seamus Coleman .
He was at least relieved that star striker Romelu Lukaku appears to have come through a full game with Greece and a short substitute stint against Russia unscathed.
And the Everton manager contrasted the approach of Belgium boss Roberto Martinez — his predecessor at Goodison — to O’Neill’s, saying: “I was pleased by Martinez that, one, Kevin Mirallas was starting (in the friendly in Russia) and, second, that Romelu was not starting.
“That’s good for us, because he played for 95 minutes in the qualification game against Greece.
“You like people to understand… not like Ireland.”