Koeman is under pressure after drawing with Granada and Cadiz this week.
But Planes says: "If Koeman will be there on Sunday? I think so, he is our coach and we have to give him support.
"The coach is always under scrutiny. But we are Barça, the best club in the world and we have a great squad.
"There are no transition seasons. We have the chance to win the championship, the squad is there."
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