Robert Kubica's father thinks the departing Williams driver will choose either between an F1 test role or racing in a series like DTM for 2020.
The Polish driver has been linked with test roles at Haas and Racing Point, perhaps splitting it with a race seat in the German touring car series.
But his father Artur Kubica told Poland's Onet: "It would be difficult to combine the role of test driver with another racing series.
"The work of a development driver in F1 is full-time."
It is believed that talks between Kubica's sponsor, PKN Orlen, and the American team Haas, are advanced.
When asked about Haas and Racing Point, Artur said: "It seems to me that of the teams you mentioned, Haas would be a better choice for Robert.
"There is hope that he can be in the race driver's seat, and on paper Racing Point looks like a worse choice.
"Lance Stroll will definitely drive irrespective of his pace, and Sergio Perez has just extended for another three seasons," he added.
"As for DTM, Robert could regain his joy of racing there. It is probably the best series after F1, but the key would be to be in a factory team."
