Borussia Dortmund is in shock.

The nightly news about the serious illness of new signing Sébastien Haller caused deep dismay for everyone involved.

Just a few hours after the morning training session, during which the 28-year-old Ivory Coast international complained of being unwell, doctors diagnosed a tumor in his testicles.

“This news today came as a shock to Sébastien Haller and to all of us.

The entire BVB family wishes Sébastien a full recovery as soon as possible and that we can hug him again soon," commented sporting director Sebastian Kehl.

Managing Director Hans-Joachim Watzke was also deeply affected.

"Of course we are all in shock," said the club boss: "Our thoughts are with Sebastien and his family.

The most important thing now is that he gets well again.”

Haller complained about being unwell after training on Monday morning in Bad Ragaz, Switzerland.

The tumor was discovered during intensive medical examinations during the course of the day.

The 28-year-old has already traveled back to Dortmund.

"We will do everything in our power to ensure that he receives the best possible treatment," said Kehl.

According to BVB, "further examinations will take place in a specialized medical center".

Only after the evening test against FC Valencia (1:3) in Altach (Austria) was the team informed about their team-mate's illness.

Even coach Edin Terzic was obviously not in the picture shortly after the final whistle: "Sébastien woke up this morning and didn't feel so good.

He trained anyway.

After that, the symptoms got a little stronger,” he replied when asked about the reasons for Haller’s surprising absence.

The goalscorer, who was signed by Ajax Amsterdam for over 30 million euros, had only started preparing for the new season a week earlier.

He is considered BVB's king transfer this summer and is intended to close the gap in the center of attack that arose after Erling Haaland's departure to Manchester City.

At his first public appearance in the black and yellow jersey last Sunday, Haller exuded confidence: "I'm not coming to Borussia Dortmund as someone's successor, but because the club needs my quality.

So I will do my best to give back the confidence.”

The first training sessions with Haller strengthened Marco Reus in his belief that his new strike partner could soon step out of Haaland's long shadow.

"He's not as fast as Erling, but he's a giant striker.

We didn't lose many weapons," commented the BVB captain on Saturday and asked for patience with the newcomer: "Let's give him a little time to settle in."