The midfielder has only played 62 minutes for the Blues since returning from the Africa Cup of Nations at the start of February.
Gana wasn’t considered for the trip to Stoke City just days after jetting back from duty with Senegal.
He was then an unused substitute in Everton’s 6-3 demolition of Bournemouth and, after starting in the goalless stalemate at Middlesbrough last time out, was replaced just after the hour mark.
“It’s normal,” Gana told evertontv. “When you go away for the African Cup you need time to come back into the team. The weather is not the same, the players [you are playing with] aren’t the same.
“Playing four games [at the tournament] can be tiring, so you need some time when you come back. That’s why the manager has done it like this.”
Koeman himself believes that Gana will have benefitted from Everton’s two-week break in the fixture schedule since the trip to the Riverside Stadium last time out.
The Dutchman said: “I wasn’t happy with his performance against Middlesbrough and I spoke to Gana who said he was still a little bit tired from the African Cup.
“But what I saw from Gana last week and this week is that he is at the level we expect and what he saw from him at the beginning of the season. He’s back and that’s important for the team.”