AC Milan were held to a 1-1 draw at Parma in Serie A on Saturday after veteran defender Bruno Alves scored with a majestic free kick for the midtable hosts with three minutes left.
The 37-year-old Portugal defender curled his effort over the wall and squeezed it between Gianluigi Donnarumma and the near post to give Parma a deserved point and hand Milan a setback in their quest to qualify for next season's Champions League.
Milan are fourth, in the lowest of the Champions League slots, with 56 points, two ahead of Roma who were playing at Inter Milan later on Saturday, and their performance frustrated coach Gennaro Gattuso.
"I expected more," he said. "In the first half, we were lethargic, they were compact and we couldn't find any space.
"We did well to unlock the match but then we were naive in giving away the free kick from which they equalised."
He refused to blame the hot conditions for their display, and added: "It was the same for Parma; at times they were angrier than us."
Even after Castillejo broke the deadlock, Milan looked far from comfortable. Luca Siligardi hit the post from a narrow angle after heading the ball past Donnarumma and Kucka was again close with a dipping volley before Alves finally equalised with his fourth goal of the season.