Shunsuke Nakamura admits Celtic must up their game considerably for their Champions League meeting with Manchester United at Old Trafford.
Nakamura is quoted as criticising Celtic's play
"We need to improve as a team before this game because we're not playing well enough for the Champions League," the midfielder told The Sun.
"We have brought in two or three new players and, unfortunately, we still don't know each other well enough.
"So far this season, I don't think we've been playing well as a team."
It took a late goal by new signing Jan Vennegoor of Hesselink to secure the victory away to Aberdeen on Saturday that kept Celtic top of the Scottish Premier League.
Right now, I think a draw would be an important result for us
"Our last game against Aberdeen brought a win, but we didn't play well," said Nakamura.
"For me, we played too many long balls to Jan Vennegoor of Hesselink and that's not good enough for the Champions League."
Nakamura believes a point from their Champions League opener would be a satisfactory result.
"For this game, we can't go down to Manchester and attack, attack, attack," he added.
"It's hard to win there, so for us it will be vital to defend in this game.
"Right now, I think a draw would be an important result for us."