Haga crashed twice en route to the fastest time in the tricky conditions but he remained on top, turning a best lap of 1:50.595, some 13 seconds off his lap record from last year.
Xaus rode the Sterilgarda Go Eleven Ducati to the next best time, holding off Ducati Xerox’s Troy Bayliss, the Aussie looking to try and wrap up the World Championship this weekend.
Behind Bayliss came Haga’s teammate Troy Corser, the Yamaha man set to become the first rider in series history to start in 300 World Superbike races.
Leading the provisional second row is Hannspree Ten Kate Honda’s Ryuichi Kiyonari, the Japanese rider besting Spaniards Gregorio Lavilla and Carlos Checa. Robby Rolfo rode his Honda CBR1000RR to the eighth best time over Kawasaki’s Regis Laconi and Ventaxia VK Honda’s Chris Walker.
In addition to Haga, Tamada (twice), Checa (twice), Jakub Smrz, Corser, Matt Lynn and Max Neukirchner all suffered crashes in the wet session.
In World Superport action, Parkalgar Honda’s Josh Hayes ended the first session in 13th place in what is his World Supersport debut at a circuit he’d never seen prior to arriving in Italy.
“The weather is wet and cool, which combined with a new team and bike, has made Josh’s job as difficult as possible today,” said team manager Simon Buckmaster in a team release. “He has handled the pressure well and despite a weather-induced crash this morning I think he has shown real promise. He is ahead of World Champion elect Andrew Pitt, so that is a simple measure of his ability.
“I think there is a lot more to come from Josh as he gels with the bike and learns the circuit – he is quickest in the first sector, fourth in the final sector and his ideal lap time was half a second faster than his qualifying. He needs to work on his middle sector and he will be well inside the top 10.”
Hayes’ best lap was a 1:57.382 – some three seconds off the best lap set by Mattieu Lagrive.
1. Noriyuki Haga (Yamaha) 1:50.595
2. Ruben Xaus (Ducati) 1:50.879
3. Troy Bayliss (Ducati) 1:51.146
4. Troy Corser (Yamaha) 1:51.228
5. Ryuichi Kiyonari (Honda) 1:51.419
6. Gregorio Lavilla (Honda) 1:52.012
7. Carlos Checa (Honda) 1:52.143
8. Robby Rolfo (Honda) 1:52.407
9. Regis Laconi (Kawasaki) 1:52.423
10. Chris Walker (Honda) 1:52.466