Manchester City's 4-0 away win meant the second leg of the last-16 tie was almost a formality, with Pep Guardiola resting several first-team players, including Sergio Aguero.
They led through a Gabriel Jesus opener from Bernardo Silva's cross. But Mohamed Elyounoussi lashed home a leveller and then set up Michael Lang for a shock Basel winner.
Here's five things we learned from the game...