The Toffees are closing in on Diaz in a deal which will see a fee of around £21m paid to FC Porto, while James Rodriguez will go to the Portuguese side on loan.
The clock is ticking on the transfer window though and Everton do not want to risk missing out on Diaz.
As such they could choose to put him through his medical checks in Portugal in order to speed up the transfer.
Everton are in the process of finalising their agreement with Porto and it remains to be seen how long thrashing out the remaining details of the deal takes.
Diaz shone at the Copa America for Colombia in the summer and Rafael Benitez will be looking for him to hit the ground running at Goodison Park.
He has already brought in Andros Townsend and Demari Gray, but wants Diaz throwing into the attacking mix too.
Benitez has also ruled out a departure for Brazil international Richarlison, who has been linked with Paris Saint-Germain as a potential replacement for Kylian Mbappe.
