Januzaj was a constant thorn in Atleti's side, hitting the post early on, but the first major chance fell to Yannick Carrasco as he broke through on the counter down the right, but his effort also hit the woodwork.
Atleti continued to grow into the game and even began to dominate at one stage, but it was Belgian winger Januzaj who then broke the deadlock. Real Sociedad attacked down the right, with Mikel Merino's skill in the middle allowing him to spread the ball for Joseba Zaldua to cross to Januzaj, who rose above three Atleti defenders to score with his head.
The Copa del Rey represented Atletico's best chance of a title before this tie, but the defensive woes which have plagued them all season struck again in the north of Spain one minute into the second half. Felipe, starting in the absence of the suspended Jose Maria Gimenez and the injured Stefan Savic, took too long on the ball and Sorloth robbed Atletico's last man of possession and slotted beyond Jan Oblak.