Paris Saint-Germain winger Angel Di Maria says reports of the decline of Cristiano Ronaldo are "exaggerated" and he does not understand the questioning of his former Real Madrid teammate.

After an outstanding 2016, Ronaldo, 32, has had a more difficult start to the new calendar year, being blamed by some local fans and pundits for Madrid's poor run of results last month, including their exit from the Copa del Rey to Celta Vigo.

The Portugal captain was whistled by the Santiago Bernabeu crowd during Madrid's most recent game, although he then reacted with a goal and assist in the La Liga leaders' 3-0 win over Real Sociedad.

Argentina international Di Maria told Marca that his compatriot Lionel Messi has been through the same in the past and that it is only a matter of time before Ronaldo starts to "spark" regularly once again.

"It is exaggerated," Di Maria said. "He has given so much to Madrid, as others have. He has won two Champions Leagues and people forget that a bit, they always want more.

"The same has happened with Messi, people say he's not scoring enough, he's not like he was before, but overnight something sparks and the goals start to flow. I don't understand how people can question Cristiano."

Cristiano Ronaldo has been blamed by some local fans and pundits for Real Madrid's poor run of results last month. Denis Doyle/Getty Images

Di Maria has experience of being whistled by the Bernabeu crowd, reacting at one point with a rude gesture to the crowd.

He said players react differently to such treatment, pointing out, for example, that Madrid's Karim Benzema is better able to deal with the criticism than Danilo.

"Some players are mentally stronger," he said. "I see Benzema as very strong -- even though this happens, he likes to play and enjoy himself. Danilo looks a bit different, it's a bit harder for him, and his head affects him a bit more. He must think about enjoying himself and being positive when he is playing.

"It happened to me many times, I had some ugly moments at Madrid, but it all changed and when I left Madrid in the end I was much loved."

Di Maria was sold by Madrid president Florentino Perez to Manchester United just months after being named Man of the Match in the 2014 Champions League final win over Atletico Madrid.

The 28-year-old said he remains in close contact with some of his former Madrid teammates and is "eternally grateful" for his time at the club.

"There are people who miss me [at Madrid], and also some who don't, but that is football," he said. "Madrid gave me the chance to reach the very top, to be among the world's best XI that year. They gave me everything, so I will always be eternally grateful."