The Nigerian fell to the floor unchallenged in the first half of the match - which Olympiacos lost 3-0 - and received treatment on the pitch before being carried off a stretcher after regaining consciousness.
Olaitan, who joined the Greek Super League leaders ahead of the current campaign, was taken to hospital and the agency that represent him have confirmed he is making a good recovery.
In a statement they confirmed: "We are pleased to inform you that, under the first medical reports there is no sign of a serious medical condition.
"However, as a precautionary measure he will remain in hospital for the next few days to undergo further tests.
"Michael is well and sends his best wishes to all those who have shown great interest in his health.
"He is eager to return to the pitch as soon as possible."
Olaitan has scored 11 goals in all competitions for Olympiacos this season and was part of the side that beat Manchester United 2-0 in the UEFA Champions League last week.
