Jonathan Rea has lost ground in the fight for the 2011 World Superbike Championship after coming away with a sole sixth place finish at Monza.

The Castrol Honda rider had started on the front row of the grid, but found himself lacking straight-line speed as he lost touch with the leaders, the Northern Irishman's progress coming late on as he passed Troy Corser for an eventual sixth.

Hoping for better from race two, Rea lasted as far as the first corner when he was knocked down by Carlos Checa, whose attempt to pass up the inside instead results in contact.

Coming twelve months after he was eliminated in a similar accident at the same corner, Rea was disappointed with the meagre returns from his weekend.

"Frustrating really is the word, especially in race one when we just didn't have the speed on the straight," he said. "I could match the lap times when I was on my own and able to run the right lines. But as soon as I got involved in a race with anyone who slowed me down in the places I was fast, I got forced off the line and lost the speed. Sixth was OK but certainly not what I'd hoped for.

"I'll have to see the footage of race two to find out what really happened, but I feel like I got clipped from the inside which forced me up and into the guy on the outside.

Despite the results, Rea retains fourth in the standings heading to the next round at Miller Motorsports Park, where he will test prior to the race weekend.

"We're going to Miller next, which has another long straight, so I hope the guys back at base can find something. Luckily, we're testing there the week before the race so I hope that gives us at least a chance to do better than last year."