Alonso has already claimed five podiums for Aston Martin this season in seven races.
The two-time world champion is showing no signs that he's considering retirement either, with Alonso reportedly keen to renew his deal with Aston Martin.
Alonso the gladiator
Speaking during the Sky Germany broadcast for the Spanish Grand Prix, Rosberg explained: "You have to say that it's extraordinary, his ability to have such an overview during the race while driving at full throttle.
"It's somewhat comparable to Michael Schumacher, who was also extremely strong in that regard."
Rosberg had even more superlatives to throw Alonso's way, making his admiration for the Spaniard's form clear to see.
“Fernando is an absolute gladiator.
"He gives it his all every lap, and I've always had tremendous respect for that.”
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