The in-form Dani Pedrosa celebrated this week's signing of a two-year contract extension with Honda by setting the fastest time in practice for the Aragon Grand Prix.
The Spaniard, second in the MotoGP championship standings and bidding for a third straight victory after wins in San Marino and Indianapolis, was more than four-tenths of a second quicker than Ducati's Nicky Hayden in the dry morning session in his home country.
Championship leader Jorge Lorenzo, who has a 63-point advantage over compatriot Pedrosa with six races remaining, was third fastest, 0.01 seconds behind American Hayden.
Rain soaked the new track to the north-east of Madrid for the afternoon session and none of the riders came close to matching Pedrosa's earlier time.
Australian Casey Stoner, who was fourth in the morning session, was quickest in the wet ahead of Lorenzo in second and Hayden in third.