Noriyuki Haga is confident he has the pace to challenge for victory in both World Superbike Championship races at Assen, but only if he can cure his Ducati Xerox's grip problems.

The championship leader hasn't shared the pace of key rival Ben Spies for most of the weekend, although much is being pinned on his race pace having destroyed the opposition, including Spies, last time out in Valencia.

Shrugging off an earlier a accident in final free practice, Haga would go on to qualify within touching distance of the American on the outside of the front row in fourth.

Even so, with a best lap that is some six tenths down on Spies, Haga concedes he has been having problems with grip, something he is hoping to overcome in the short warm-up before the races.

"Unfortunately at the end of the free practice session I came off; I lost the front for no particular reason going into the corner, which was a bit of a surprise but I wasn't hurt and it did not affect my performance in Superpole. I'm not so happy with the level of grip but I think that it is something we can resolve in the morning.

"For the tyres there is only one option for tomorrow so we are sorted there. I can tell that tomorrow we'll have two tough races as the times are all very close but I feel we are in a position to fight to win both."

With Jakub Smrz up in second position, it was a good session for Ducati, Michel Fabrizio adding to their promising results with a run to fifth on the grid, marginally behind Haga.

"The second qualifying tyre that I used during the Superpole, in the last session, had a bit more grip with respect to the first but I didn't feel right with the general set-up of the bike.

"We still haven't totally understood the problem but I wasn't able to give 100 per cent as it felt like I was opening the gas but the bike was drifting. Having said that I am on the second row tomorrow, and even though I hoped to be further forward, I guess I'm fairly satisfied."