The captain of the Mexican national side was in no doubt when asked for his opinion on the two players, saying: "For me, Messi is the best ever, that's the truth. I've even told him as much when I've played against him".
"Nowadays I still don't think we realise how what it is to face Lionel Messi, or to have been able to play during the same period as him and Ronaldo too. These two giants of football," Guardado explained.
The former PSV man admitted that playing against the best contributed to his decision to return to La Liga. "It's a reason to come back to Spain, to play with the best. Messi is one of them, well, he's the best for me at the moment," the 31-year-old added.
Guardado has faced Messi on numerous occasions during spells at Deportivo La Coruña, Valencia and now Betis, as well as at international level, so he is well placed to judge the Argentine's ability.