Luiz Razia, Marussia's second race driver for 2013, has been left out of this week's testing in Barcelona.
The situation is causing alarm within Brazil's F1 media ranks, and raising doubts about whether the 23-year-old's new contract is now in doubt, or whether Max Chilton is simply the clear and favoured 'number 1'.
Brazilian Razia was scheduled to run for two of the four days in Spain, but Marussia said the programme was changed to exclude Razia because it "made sense to keep Max in the car for consistency".
"Max has done a great job over the last three days," team boss John Booth said on Thursday, "and we've certainly benefited from the consistency this has provided."
Obviously, the situation has triggered rumours.
"It is believed bureaucratic issues have hindered the payment of (Razia's) sponsorship to Marussia," read a report by the Brazilian news agency Agencia Estado.
Razia told O Estado de S.Paulo correspondent Livio Oricchio: "Sometimes we have to live with these situations.
"But I don't care whether I have the same number of (test) days as Chilton. In the other series I've competed in, I haven't needed much time to get used to a car."
Veteran journalist Oricchio has another theory about Chilton's prominence.
"Friends in the paddock have told me that Max Chilton's father is acquiring a portion of Marussia at the end of each of the three seasons of his son's contract.
"It is known that their investment in Marussia is far greater than that of Razia."