"The dominance of England is in question," he told Arsenal Player. "We see that with the other countries improving.
"If Stuttgart win, the Germans push their seven teams through to the next stage of [both] European competitions. The Spanish have pushed their four teams through in the Champions League.
"It's not a coincidence. We need to be conscious of that. Is it because the Premier League is so difficult in every game? Maybe. We have to have a deeper look at that."