Vargas' attack efficiency has slipped at Shanghai Port, according to sources close to the situation.
The Brazilian striker, who signed for Shanghai Shenhua in January, has struggled to find his form since arriving in China's top flight.
He scored just one goal in six games before the Chinese Super League resumed last month, and has been unable to convert any of his chances since then.
Despite this, Vargas is still expected to play a key role in Shanghai Shenhua's bid to win the league title.
But with his performances in recent weeks, there have been concerns about whether he will be able to deliver on that promise.
One source said: "There have been some issues with Vargas' fitness and conditioning, which could be affecting his performance on the pitch."
Another added: "It's not just about the physical aspect of the game, but also about mental strength and determination.
If Vargas can't get back into the rhythm of things, it could be a real problem for Shanghai Shenhua." Despite these challenges, Vargas remains a popular figure among fans of the club.
Many believe that his leadership qualities and experience on the pitch make him a valuable asset to the team.
And while his performances may not be as impressive as they were earlier in the season, many hope that he can bounce back and continue to contribute to Shanghai Shenhua's success in the coming months.