The Serb joined the Portuguese giants on a season-long loan.
He told Alo!: “Werder, whose coach [Florian] Kohfeldt is a great friend of Klopp, has been in the story for a long time, but I did not see a perspective there.
“Borussia [Monchengladbach] was a realistic option. [Valentino] Lazaro and [Breel] Embolo praised their coach, [Marco] Rose, to me.
“This attempt did not yield results, because they failed to sell the currently injured [Denis] Zakaria, but I believe that one day I will cooperate with Rose.
“I wanted to be at a stable, ambitious club that plays in the Champions League, and Porto is just that.
“While I was waiting for the flight to Oslo with the national team in Copenhagen, all the details with the 'Dragons' were settled.
“Immediately after the break, there will be a derby with Sporting, and then temptations in the Champions League – [Manchester] City, Marseille and Olympiakos. I believe that I will fight for a place with coach Sergio Conceicao and contribute to success.
“I am convinced that it is the right choice, and the Portuguese club were in a hurry to register me for the Champions League, which they did in the end."