Brawn, now the Formula 1 managing director motorsports, wrote in his Formula1.com column that Hülkenberg was next in line to replace Michael Schumacher at Mercedes should Hamilton have elected to remain with McLaren.
His comments come after Hülkenberg made his F1 return with Racing Point, qualifying third at the 70th Anniversary Grand Prix and finishing seventh.
Outclassing team-mate Lance Stroll for large parts of the weekend, Hülkenberg dropped behind the Canadian after severe vibrations on his left front forced him to pit in the closing laps.
Brawn wrote: "It was going to be an incredible physical challenge for Nico Hulkenberg and I don’t know how much he hurt at the end of the race, but it was great performance all weekend by someone who had just been dropped in the deep end.
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