Dutchman Koeman is clearly not afraid to rattle cages and with Everton flying high in the Premier League, Barkley has been warned that he is no automatic choice.
"There was a reason to take Ross Barkley off at halftime. He didn't play well, lost too many balls. Players of that quality can't lose those kind of balls," Koeman, whose side are third in the Premier League after four games, said.
"I had a talk with Ross, he needs to improve and we will see at the weekend.
He understands, we showed him the clips and there is no escape."
Barkley is still to deliver fully on his promise and failed to make new England manager Sam Allardyce's squad for their World Cup qualifier against Slovakia this month.
Against Sunderland he lost possession 11 times in a woeful first half, looking bereft of confidence.
"You look to his qualities he needs to be the key player between defenders and strikers, in a position to create and defensively be part of a team -- in all aspects he can and needs to improve," Koeman said.
Gareth Barry is in line to make his 600th Premier League appearance against Middlesbrough.
"It is amazing, 19 seasons in a row. That is fantastic," Koeman said of the former Aston Villa and Manchester City player.
New signing Enner Valencia could make his debut after signing from West Ham United last month.
(Reporting by Martyn Herman; editing by Clare Lovell)
