Borussia Dortmund coach Thomas Tuchel has denied reports of an internal power struggle at the Bundesliga side after he was not involved in the signing of Swedish youngster Alexander Isak until the deal was almost done.

Reports from Germany suggested Tuchel's relationship with sporting director Michael Zorc and chief executive Hans-Joachim Watzke has turned sour.

Nevertheless, Tuchel is adamant there was nothing strange about his involvement in the signing of 17-year-old striker Isak as he often leaves most of the legwork to others when it comes to promising youngsters.

"There are transfers where the coach is involved right from the start," Tuchel told reporters. "We are talking about transfers that look at the short term, with players who improve the team right away. The coach plays a big role in those transfers.

"But there are also deals - like Isak's transfer - where the scouting department and sporting director Michael Zorc do a lot of work before the trainer has to get involved. It was the same with [Ousmane] Dembele and [Emre] Mor. Our scouts saw these guys in action and then made a recommendation. I only enter the picture later in the deal.

"These reports about a tense relation are nothing new and I am in no mood to keep denying this time and time again.

"We work together very professionally and friendly. I can only reiterate that I am happy here at Dortmund and I enjoy coaching these players every day.

"I must admit that I did not really know Isak. But when they introduced him to me, I saw that the transfer made 100 per cent sense. 

"Alex is a very strong striker, who can play with his back toward goal and is strong in the combination. He scores a lot of goals, so it is great to have him here. He is feeling even better than before after taking part in his first training.

"The signing of Isak makes perfect sense. This gives the club a long-term solution for the position of striker. Isak is a very talented player. We needed someone behind [Pierre-Emerick] Aubameyang following Adrian Ramos' departure. It is completely logical for BVB to bring in a youngster for that role."