Nico Rosberg claimed Carlos Sainz is "trying to get a couple more million" out of Red Bull after spotting the Formula 1 star's father in conversation with Christian Horner.
Sainz is a contender for the seat currently occupied by Sergio Perez. Red Bull won't be making a decision any time soon, but team principal Horner admitted this weekend that talks had been held with Sainz.
The Spaniard is leaving Ferrari and has started the season in fine form. But Perez has also been performing well and Red Bull say that, for now at least, the seat alongside Max Verstappen remains the Mexican's to lose.
Assessing Perez's situation before Sunday's race in Shanghai, Rosberg said Perez "need to behave" and be a good wingman to Verstappen if he is to keep that seat. And he also told Sky Sports viewers what he had seen in the paddock the previous day.
He said: "You know that they have an offer out to Carlos Sainz and I saw daddy Sainz speaking to Christian Horner yesterday because Christian Horner has apparently been a bit stingy on the offer. So, they're trying to get a couple more million out of him!"
Red Bull adviser Helmut Marko claimed last week that the team could not match a "lucrative" offer that is already on the table for Sainz from newcomers Audi. The German carmaker made the 29-year-old their top driver target a long time ago.
Horner said he did not know the details of that Audi offer but claimed Sainz would prefer to join Red Bull anyway. The team boss said: "As you can tell with the level of interest that we have had from other drivers in our seats, for a driver of Carlos' calibre, he wants to be in a winning car.
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"And whilst we have one seat available for next year, his target, inevitably, is that seat. But his problem is that Checo [Perez] is in that seat and he's doing a really good job so for us as a team. It's a luxury situation but one that we don't need to rush and we'll take our time to consider the options."
Verstappen won the Chinese Grand Prix with ease but Perez was not able to back him up with a one-two. He had to settle for third place as Lando Norris drove the wheels off his McLaren to wedge himself between the Red Bulls.
It was a tougher day for Sainz who missed out on the podium for the first time this year. He had to settle for fifth, behind Ferrari team-mate Charles Leclerc, as they both struggled for pace throughout the race.