Spanish winger Asensio cost Real a mere 3.5 million euros from Mallorca in 2014 and entered the game only in the 79th minute but played a decisive role in Cristiano Ronaldo and Marcelo each scoring late on to give the European champions the edge in the tie.
Paris St Germain spent 400 million euros ($498 million) on Neymar and Kylian Mbappe last year but it was Real Madrid's bargain signing Marco Asensio who stole the show when Real beat the Parisians 3-1 in Wednesday's showcase Champions League last-16 first leg.
Spanish winger Asensio cost Real a mere 3.5 million euros from Mallorca in 2014 and entered the game only in the 79th minute but played a decisive role in Cristiano Ronaldo and Marcelo each scoring late on to give the European champions the edge in the tie.
With less than three minutes on the pitch the 22-year-old tore into the area from the left wing to find Cristiano Ronaldo, who bundled the ball into the net off his knee to put Real ahead for the first time in the 83rd minute.
The Spain international then flew down the left wing again to drill the ball back for Marcelo to strike the third goal, requiring PSG to win the second leg by at least two goals if they are to avoid an embarrassing exit from the competition at the last-16 stage for a second consecutive season.
PSG suffered a humiliating elimination from the tournament by Barcelona last season after losing the second leg of their tie 6-1.
Their signing of Neymar from Barca for a world record 222 million euros looked like a statement of intent to make their mark on this season's competition.
The Brazilian has scored 28 times for PSG but was less effective in their biggest game so far and picked up an early yellow card for fouling Real defender Nacho Fernandez.
Mbappe will cost the Qatari-backed club 180 million euros when his loan deal from AS Monaco expires in June. He forced the opening goal scored by Adrien Rabiot.
He squandered a clear chance to restore his side's lead in the second half, however, firing straight at Real goalkeeper Keylor Navas after being played in by Neymar.
PSG coach Unai Emery said his side had been unfortunate and criticised referee Gianluca Rocchi for awarding Real a penalty for Giovani Lo Celso's shirt pull on Toni Kroos and not penalising Sergio Ramos when Rabiot's shot hit the Madrid captain's arm in the area in the second half.
"We played with character but the late goals are hard for us to take," Emery told reporters.
"We deserved a better result. You could say the game was decided by the small details, the referee didn't help us. From the start of the game he gave more decisions to Real. I don't think it was a penalty (for Real) and then there's the Ramos handball. It's not the same criteria."
