The Australian has backed the Juventus star for more individual silverware after his bold move to Serie A.
Both players are currently locked on a record five Ballon d’Or titles and it is the Argentine that appears on track to pick up his sixth later this year.
Messi scored 36 goals in La Liga this season as Barcelona claimed another league title and he chipped in with a further 12 strikes in the Champions League.
Though Ronaldo’s numbers at Juventus have paled in comparison with the 34-year-old bagging 15 fewer league goals in Serie A, Cahill believes the fact he has been able to transition to another league so successfully deserves recognition in the form of the Ballon d’Or.
“The reason why I say Ronaldo, I know people won’t agree, is because of what he’s done in Juventus,” Cahill told Alkass Sport.
“He left Real Madrid, went there and had such a massive impact on another league. I’ve never seen another player do it at Man United, Madrid for so many years.
“And I know he didn’t win the Champions League but he has such an impact in any club. If you can take players and put them somewhere at his age…
“I know people won’t agree, I just appreciate his professionalism.”
Ronaldo’s Juventus teammate Medhi Benatia unsurprisingly recently agreed with Cahill, suggesting Barcelona’s loss to Liverpool in the Champions League semi-finals may have hurt Messi’s chances.
“Ronaldo? He deserves to win the Ballon d’Or according to me,” Benatia said, per Calciomercato.
“Messi? He had an incredible season. He would deserve it too but with Liverpool beating Barcelona, I think this reduced his chances.”
PSG star Kylian Mbappe, who has scored the second most goals in Europe this season behind Messi, has backed the Barcelona star to claim the Ballon d’Or, where he finished a distant fifth in voting last year.
“The favorite is Messi,” Mbappe said.
“The elimination in Champions (League) does not change anything, he is the number one in everything.”
Both players have one more match this season, with Messi facing a Copa del Rey final on Saturday while Ronaldo and Juventus have their Serie A finale Sunday against Sampdoria.