Ko Itakura has confirmed he will not be returning to Schalke in the summer as speculation swirls over his future.
The Manchester City star spent last season on loan and helped the Bundesliga 2 side gain promotion back to the top flight.
City are reportedly demanding almost £5m for the 25-year-old however and Schalke are reluctant to pay up.
Waz reported that Schalke must decide by today, May 31 if they want to take up a €5.5million (£4.6m) option to buy.
And it seems they have decided against it - opening the door for Celtic to revive their interest.
Posting on social media Itakura wrote: "I am very grateful for my time with Schalke. It is a great club and we enjoyed a great season together. It really felt like a family.
"I will miss everyone here very much, but I wish Schalke all the best for the future. Thank you for everything
"Glück auf (good luck)."
Itakura was on a list of Celtic targets last summer and has re-emerged as a rumoured defensive option.
Ange Postecoglou is in the market for a new centre-back and it's understood that would be in addition to Cameron Carter-Vickers, rather than as an alternative.
The American is closing in on a permanent return and could join alongside Itakura or Taylor Harwood-Bellis, who has also been linked with a move from City.