Ronaldo returned for Real Madrid and it barely took him 12 minutes to find the back of the net, showing his ruthless eye for goal once again. His first goal against Apoel was that of instinct, of knowing where to be inside the six-yard box.
The rival penalty area is Cristiano's favourite place to be, even though he insists he is not a natural No 9. But Zidane exploits his star's strengths. The Frenchman is aware that the 32-year-old's physical capacities have diminished slightly in recent years and that Ronaldo has become an out-and-out centre-forward.
The long calendar is demanding, Cristiano Ronaldo has realised he cannot keep up and has agreed to be rested more regularly. His development is clear on the pitch. Real Madrid's No 7 is a more pragmatic No 9: last season, 85 per cent of his 48 goals were first-touch.
At Barcelona, Ernesto Valverde is determined to bring Messi closer to the danger area, where he can cause real damage. The Barca boss has brought back the 'false 9' employed by Pep Guardiola which saw Messi excel, becoming a legendary goalscorer.
But there are variations between Messi and Ronaldo. Against Juventus, the Argentine displayed a total version of himself. He dropped into midfield to begin moves for his teammates. Suarez and Dembele supported him out wide for Messi to offload and receive assists when offered a sight of goal, much the way it happened in Barcelona's first goal.
Messi's second goal at the Camp Nou was entirely different in that he was the last man to receive the ball. The striker cut onto his favoured left foot before firing into the bottom corner. Against Espanyol, Messi was a more static No 9: three goals, all three inside the area.
With their respective divergences, Messi and Ronaldo share an evolution. Their mileage-per-game is substantially reduced, but they remain just as much of a threat for goalkeepers. The Champions League opener has confirmed they have not lost their appetite for goal.