A fully-fit Mario Gotze would provide a huge boost for Borussia Dortmund, but Hans-Joachim Watzke has warned not to expect too much too soon.
The Germany international – who scored the winning goal in the 2014 World Cup final – returned to action in Saturday's 3-2 win over Urawa Reds, coming off the bench to mark his first appearance since January.
Gotze has been struggling with a metabolic disorder and new Dortmund coach Peter Bosz vowed to be "careful" in managing his recovery.
And chief executive officer Watzke underlined the midfielder's importance to the side.
"From his mentality and attitude to his great passion, Mario was always ready," he told Welt am Sonntag. "That was never a concern.
"However, he suffered a serious illness. We have never talked about it in detail and will not.
"Michael Zorc and I had very close contact with him over the last five months. We knew everything. The fact that it is now all going in the right direction makes us all happy.
"If Mario is fit, he is one of Borussia Dortmund's most important players."