Turkey goalkeeper Volkan Babacan says
Barcelona midfielder Arda was booed by a number of supporters during Turkey's dismal 3-0 defeat at the hands of holders Spain on matchday two.
Reports of unrest in the squad have led to suggestions that Arda will be dropped for the final group game against Pavel Vrba's side, despite Turkey needing a win to keep alive their hopes of reaching the last 16 as one of the best third-placed sides.
But Volkan has backed the former Atletico Madrid star to respond to his critics in Lens on Tuesday.
"We have a decisive game tomorrow, that's all we're focused on. Our captain will react in the best way," he said.
"I've had to criticise myself, I haven't contributed enough in my two games. But we believe we will stay here. I will contribute more."
He continued: "Unfortunately we didn't start the tournament well, but we didn't in qualifiers, either, and got the job done.
"We still have a great chance to stay in the tournament, we believe it and I hope we'll make it because we still have a long way to go.
"We played big sides in Europe and they played well defensively and offensively. We didn't expect the negative start but we still have a chance. We can make it tomorrow. Well do our best.
"We're really looking forward to going as far as possible. We've done it before. We need to reach our best level. Our ambition is to win, we are highly motivated. This is our last chance.
"We know them very well, we played them in qualifiers. They have to win tomorrow. I think it will be an entertaining game."