Manchester United and Newcastle United were among the English teams to be linked to him last summer.
But he instead moved to Borussia Dortmund, who triggered a release clause to sign him for 17.5m euros (£14.7m).
Another injury delayed his debut but he has been prolific since getting into the team – with 24 goals in 34 games.
Ten of those have come in the Champions League, in his debut season in Europe’s top competition, where he has outscored everyone apart from Bayern Munich striker Harry Kane (10) and Barcelona’s Raphina (11).
“I understand that my form might surprise some, but I’m not surprised,” he said recently., external
“I have had two crazy seasons, but I’ve not changed anything. I’m not working more, I’m not sleeping more, I’m not doing more video analysis.
“It’s just a question of confidence. And I have understood that at the highest level, talent isn’t enough.
“You have to push through the pain barrier in challenges, in the effort you put in, in making high-intensity runs again and again, more quickly and more frequently than your opponents.
“Perhaps that is where the change has come from.”
