Benfica striker Vangelis Pavlidis had a night to remember personally, despite his team's late collapse, scoring a first-half hat trick to put his side 3-1 up.
Barcelona have secured their passage into the last 16 of the Champions League with six wins and one defeat to date. Liverpool, who beat Lille 2-1, top the league stage from Barca in second, and are the only other side to be assured to skip the playoff round at this stage.
In the 64th minute, Benfica goalkeeper Anatoliy Trubin tried to clear the ball from what should have been a regulation goal kick.
Wojciech SzczÄ™sny came out of retirement to answer Barcelona's call after Marc-André ter Stegen was ruled out for the season with injury, but he might be regretting it tonight in Lisbon after a howler of epic proportions.
After hours: January 17 at 6:56:28 PM EST