As Toro Rosso mulls who could eventually replace Pierre Gasly at the US GP next week, one potential driver who has been excluded is Robert Kubica.

Red Bull will differ to Honda on the decision to have Gasly either race in Austin or in Japan, where he is in the running for the Super Formula title.

In the event that the 21-year-old F1 rookie, who replaced Daniil Kvyat in Sepang and at Suzuka, isn't chosen to race alongside the Russian in Austin, Red Bull must find a one-off replacement.

Kubica, who is fighting for a sensational comeback to Grand Prix racing after a seven-year absence due to an injury sustained in a rally crash in 2011, was apparently under consideration, along with Sebastien Buemi.

According to Germany's Auto Motor und Sport however, the Pole's management team - which includes reigning world champion Nico Rosberg - is excluding a one-off return because it would imply the reimbursement of a huge lifetime insurance payout Kubica received for being permanently unable to race in F1.

While a full-time return would likely be financially viable, Rosberg insists that Toro Rosso's one-race opportunity would be too great a risk for Kubica.

"If you are thrown into deep water in a strange car without a test, you can only lose," said the German.

"It is better to keep going for the Williams opportunity."

Kubica is set to test for Williams in a 2014-spec car in the coming week along with Paul di Resta as the two men, along with Felipe Massa, are under consideration for the coveted F1 seat for 2018.

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