Koeman issued an ultimatum to Barkley at the end of last season, telling the 23-year-old he must sign a new deal or be sold. Rooney won't be able to bring trouble because the age has catch up with him thus why he was released for free by Manchester United.
Carrick has been a part of five Premier League titles, an FA Cup victory and a Champions League title.
Wayne Rooney hopes to force his way back into the England squad after completing a move back to boyhood club Everton, something he believes would have been impossible if he'd moved to China.
Carrick joined United from Tottenham in 2006 and after Rooney's departure is the longest serving player at Old Trafford.
He's thought to have taken a huge pay cut to re-join the club he left 13 years ago. "I'd rather have several players scoring 10 goals".
"I can not wait to run out at Old Trafford in front of 75,000 fans, but before that pre-season is where the hard work starts and I am looking forward to that first training session".
The Toffees received a warm welcome after arriving in Dar es Salaam on Wednesday with large numbers of Tanzanian football fans eager to greet Rooney and his new team-mates. I had a bad game at Watford away and that was it.
"I understand why he has gone and we all fully support him and wish him well", the midfielder admitted.
"Of course Gareth had to make a decision..."