The incident in question took place during the first half of Saturday's 0-0 draw between city rivals Atletico Madrid and Real Madrid.
Luka Modric looked to set Ronaldo away on the counter, only for Juanfran to outpace the Portuguese and get across to clear away the danger.
It was a sad sight to see Ronaldo beaten in a foot race by a defender who has never been renowned for his pace.
According to in infographic produced by 'Movistar+', Juanfran reached a top speed of 33.8km/h during the race, whilst Ronaldo could only manage 32.8km/h. That stat paints a sorry picture as far as Ronaldo's physical decline is concerned, especially when you consider that just a few years ago, the same measure considered him the fastest player in the world.
¿Llegó el declive físico de Cristiano? pic.twitter.com/1stBviKBel
— Señor Amaro (@MiguelMoreno07) 19 November 2017
que rapido es CR7 https://t.co/d3hbCAU1z2
— FCBarcelona (@FCB_es10) 19 November 2017