The man who succeeded Ange Postecoglou at Yokohama Marinos has conceded the club are struglling big time after he joined Celtic.
The Australian exited the Japanese club last week to become the permanent successor to Neil Lennon.
But in their first game in the post-Postecoglou era, Yokohama slumped to a 3-1 J League Cup defeat at home to Consadole Sapporo.
And caretaker manager, Hideki Matsunaga, believes the players' performances have suffered after Postecoglou opted to leave for Celtic.
He said: "The staff and players have had a very tough time mentally for the past two weeks.
"The resignation of the manager has made it difficult to adjust.
"There's little doubt that the loss of Mr Postecoglou has had an impact for sure.
"I don't want to make excuses for the defeat, but that's the way it has been. Everyone will need to raise their heads for our next game against Sagan Tosu next week."
And Yokohama's Brazilian defender Thiago Martins did little to hide his disappointment at his former manager's decision to leave for Glasgow.
He said: "To be absolutely honest, it's not been easy for us at all.
"Our manager has left and sudden changes like that can make everyone feel upset or unsuccessful. This was the result in the match out there.
"It's up to us to recover. At times like this, we have to fight together as a team."
