Karim Benzema had a point to prove. The 28-year-old striker was left out of the side that beat Atletico so impressively at the Vicente Calderon on Saturday and had to settle for a place on the bench in this match too. But he headed home the winner to overshadow Cristiano Ronaldo's return to Lisbon and seal an important win for Real Madrid.
Already two points behind Borussia Dortmund in Group F, Real really needed a win to keep their hopes of topping it alive and a defeat to Jorge Jesus' men could even have threatened their chances of reaching the last 16.
Ronaldo received a generous welcome from fans at the Jose Alvalade, having emerged through the youth system at Sporting and started his career in the famous green and white shirt.
But it was not his most memorable night. Perhaps fatigued following his hat-trick show in Madrid's 3-0 derby win, the Portuguese poked a pass through to Raphael Varane as the Spanish side took the lead - but he failed to a register a shot on target in a Champions League group game for the first time in his career at Real.
But it was not only Ronaldo. Zinedine's Zidane's side, understandably, lacked the energy of their impressive derby display and with 10 of the 11 players kept in the team (Sergio Ramos replaced Nacho in the sole change), the tiredness was evident just three nights on from that triumph.
While Ronaldo was unable to hit the heights, Gareth Bale limped off with an injury and Madrid will be sweating on the fitness of the Welsh winger with the Clasico against Barcelona coming up at Camp Nou on December 3.
Nevertheless, Madrid looked good for all three points - especially after Joao Pereira was sent off for lashing out at Mateo Kovacic in an action that was hugely exaggerated by the Croatian midfielder.
Even with 10 men, though, Sporting came back, and it was another Portuguese full-back who would end up influencing the game. Fabio Coentrao, booed by Sporting supporters due to his Benfica past, handled in the area after coming on and Adrien Silva slotted home the penalty to make it 1-1 late in the match.
All of Madrid's good work was undone in that one moment, but there was to be a happy ending after all and it came via Benzema, almost the forgotten man after Madrid played so well without him on Saturday.
The French forward brilliantly headed home a Sergio Ramos cross in the 87th minute to seal a vital victory for Zidane's side. Thus, the two players who had been expected to start for Real against Atleti but had not, had combined to seal this win.
Ramos will regain his place, but this was a point proved by Benzema. He remains important to this team - be it as a starter or as an impact substitute for Real Madrid - and once again strength in depth saw Zidane's side through yet another tough test.