Koeman spoke about the absence of Messi for Tuesday's game against Eibar in a press conference on Monday.
"Leo had a problem with his ankle and hasn't been in condition to train nor will he be ready for tomorrow, so he's had two more days off," Koeman said.
"The doctors recommended rest. He returns after Eibar. They said that a week without training will make sure he's OK to return after the game."
On Messi's interview with Jordi Evole, Koeman added: "I did not see it live but I have seen what's come out in the press and it seems good to know his opinions.
"In his care (regarding his future) I have always been relaxed and I won't be more relaxed now. I can't influence anything, I can just get the best performances in games and we will see what happens."
In the interview, Messi praised Koeman's work so far. "Of course I am grateful for what he said. He's an important player for this club, in the world of football, and anyone would like it if he said good things.
"I am still the same, though. It's a transition year and Leo is an important part of this team."