But the German said the vice-captain, who has been sidelined with a muscle issue, could return for the season's final game against Chelsea on July 22.
"My last information is from yesterday because today I didn't speak to anybody because we have training later," the manager told his pre-match press conference.
"Millie is in contention, or is pretty safe for the Chelsea game; nobody told me yet he will be available for tomorrow – and he didn't train yesterday, so that's not a good sign then.
"But it will be fine for Chelsea, I am pretty sure.
"Apart from that, no new injuries on the list, so we should have the same squad like we had for the Burnley game."
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!