Koeman has tipped Ajax, AZ Alkmaar, Feyenoord and his own team to battle it out for the title.
He said: “Feyenoord have done the most transfers, we will have to wait and see if they will be a real team, but they certainly have a side that can compete for the title.
“Ajax saw a few players go, and up until now they haven’t had real good time in the transfer market, but they always fight for the top places.
“AZ have kept a lot of their squad and bought new strikers for about 12 million euros (£8million). They have a young and talented side.
“But all in all, I think that the difference between us and those three clubs will be small.”
