Ajax, which remains winless in the competition this term, went behind after just six minutes when Samuel Dahl fired a rebound into the top-right corner with a brilliant finish after Vitezslav Jaros initially denied a header from Richard Rios.

Ajax captain Davy Klaassen squandered the two best chances as the hosts pushed for an equaliser, first seeing his effort saved by Anatoliy Trubin before sending another wide of the left post from close-range, and it was punished in the 90th minute when Leandro Barreiro secured all three points for Benfica with an emphatic strike.

Elsewhere, Mourinho's former club, Galatasaray, failed to move level with the early leader in the competition after it fell to a surprise 1-0 defeat at home to Union Saint-Gilloise.

It was an end-to-end encounter at RAMS Park, with both sides hitting the woodwork in the first half as Gabriel Sara struck the upright with a long-range strike before Ross Sykes crashed a header against the crossbar.

But the match-defining moment occurred in the 57th minute as Promise David was able to finish past Ugurcan Cakir from point-blank distance after Adem Zorgane squared the ball across the box.