Josh Hayes performed admirably on his MotoGP debut in tricky weather conditions at Valencia on Friday.

The reigning double American Superbike champion has been called up by the Monster Yamaha Tech 3 team to replace an injured Colin Edwards.

Despite no prior experience of the bike, tyres or track, Hayes was 15th and then 10th in the two practice sessions, the first of which was held on a damp track and the second in fully wet conditions.

With the best times set this morning, Hayes finished his first day as a MotoGP rider 2.5sec from world champion Casey Stoner and ahead of Yamaha test rider Katsuyuki Nakasuga, riding the factory M1 in place of Colin Edwards.

“My first day in MotoGP has been very difficult and quite scary at times to be honest. Before I went out this morning I don't think I have ever been so nervous in my life," revealed 36-year-old Hayes. "I was happy with my lap times this morning in tricky conditions but then in the full wet this afternoon it meant it was quite a scary introduction to MotoGP.

"Although I've not experienced the full potential of a MotoGP bike because of the wet conditions, it is obvious that the Tech 3 Yamaha is a very good motorcycle and the team has done an excellent job to try and make me comfortable. All I had to do was ride the machine and try to improve.

"Right now it is not so much about the set-up of the bike, it is just me learning the bike and I will continue that process tomorrow. I just hope that at some point I will get to have a dry practice so I can get to grips with the carbon brakes.

"I don't want to be going into the race on Sunday having to learn to ride in the dry and also adjust to the carbon brakes after two wet days. That would be the worse scenario for me but I enjoyed today a lot. It was a great experience and once again I want to thank everybody at Yamaha, Tech 3 and Monster that made this possible.”

Regular Tech 3 rider Cal Crutchlow was tenth fastest, 1.5sec ahead of Hayes.