Athletic Bilbao coach Marcelo Bielsa says the club must wait to feel the full effect of losing key man Javi Martinez to Bayern Munich.
The €40 million transfer of the versatile 23-year-old, who can play as a defensive midfielder or centre-back, brings to an end a month-long transfer saga between Bayern and Athletic.
Speaking ahead of Thursday's Europa League qualifier against HJK Helsinki, Bielsa conceded it was a big blow to lose a player of his calibre.
"Athletic lose the contribution of a fantastic player, that is the result," he said.
"However, he virtually played no games in pre-season and the team was constructed without him.
The Argentine trainer remained philosophic by adding: "The reality is that the decision is one that everyone knows and only time will tell how it affects him and us."
Bielsa also stressed the importance of not having a bad result in the second leg of their qualifying match against Helsinki, though the tie seems a foregone conclusion, with Athletic holding a 6-0 aggregate lead.
"A good performance does not improve anything, but a bad performance would worsen the situation we are in," he said.
Athletic opened their La Liga campaign with defeats to Real Betis and Atletico Madrid.