Madrid - First-half substitute Nacho was the unlikely hero with the only goal of the game as Real Madrid beat Paris Saint-Germain 1-0 on Tuesday to seal their place in the Champions League last 16.
The defender had only been on the field for two minutes as an emergency left-back in place of the injured Marcelo when he took advantage of a defensive mix-up in the 35th minute to slot past stranded PSG goalkeeper Kevin Trapp and score the only goal of the game.
The result allowed Rafael Benitez's side to become one of the first teams to guarantee their place in the knockout rounds as they maintained their unbeaten record this season and inflicted a first defeat on PSG since Barcelona eliminated the French champions from this competition in April.
However, PSG only have themselves to blame for losing after missing a host of chances in a first half they dominated.
With Shakhtar Donetsk beating Malmo 4-0 in Ukraine in the night's other game, Laurent Blanc's side remain four points clear of the teams below them and so should still comfortably join Madrid in the next round, but they are likely to have to settle for second place.
There was particular pressure on the visitors to show they could genuinely compete with one of the continent's finest in their own backyard after they lacked inspiration in a 0-0 draw with an injury-hit Real in France a fortnight ago.
And to be fair to PSG, they immediately took the game to their hosts, controlling possession and overcoming the loss of influential midfielder Marco Verratti to what appeared to be an ankle injury after just 17 minutes.
Back at his old home ground, Angel Di Maria played in Serge Aurier and his cutback picked out Blaise Matuidi for a first meaningful shot at goal, although his effort on his weaker right foot was easily saved by Keylor Navas.
Zlatan Ibrahimovic, so disappointing in the reverse fixture, then curled a shot agonisingly wide and the Swede also hammered a long-range free-kick inches past the post with Navas beaten just before the half-hour mark.
The crucial moment in the game arrived shortly after, with Nacho being sent on to replace Marcelo after the Brazilian pulled up injured.
Two minutes after that, the 25-year-old defender put his team in front, with the aid of the PSG defence.
When a Toni Kroos shot struck Thiago Silva and looped up into the air, Trapp came racing off his line towards the ball but then stopped, allowing Nacho to sidefoot a first-time effort into the unguarded net from the left side of the box.
The goal came utterly against the run of play, and to their credit PSG did not let their heads go down.
Adrien Rabiot sent a controlled volley with his left foot against the base of the post from 25 yards before somehow both Edinson Cavani and Ibrahimovic failed to connect with an inviting Maxwell cross from the left.
Worse was to come as Cavani passed up the best chance to fall the visitors' way yet, squandering a glorious opportunity to score after a Di Maria pass had left him through with just Navas to beat.
There was a vast improvement from Madrid in the second half and most of the chances were theirs, with Trapp saving from Isco, twice, and Kroos.
However, there was to be more agony for Paris as Di Maria crashed a free-kick off the top of the bar and over in the 89th minute, as the home fans breathed a sigh of relief.