The Castrol Honda team will be without both of its regular riders for the ninth round of the World Superbike Championship this weekend at Silverstone after Ruben Xaus joined Jonathan Rea in being sidelined for the event.

It had already been confirmed that Rea was to miss a second successive meeting and be replaced by Alex Lowes [see separate story HERE], but the team has now revealed that Xaus will also be forced to sit out the British meeting.

The Spaniard was involved in a first lap crash during the opening race at Brno earlier this month, with initial scans suggesting there had been no major injuries.

However, after continual back pain, Xaus underwent further tests last week which revealed a fractured vertebra that will rule him out of the Silverstone meeting, although he hopes to be able to return to action at the Nurburgring in September.

Xaus' injury will mean a return to the Ten Kate-run team for Australian rider Karl Muggeridge, who spent two seasons in World Superbike's with the team after lifting the World Supersport crown in 2004.

The 36-year-old is currently second in the IDM German Superbike standings having taken the title in his debut year in 2010.

"I was actually on holiday with the family in Italy when the call came through from Ronald [Ten Kate], but I'm really happy to get this opportunity to join the team again," he said. "I actually rode for the Castrol Honda British Supersport team way back when, so it's good to be back with that iconic racing name again, too.

"The World Superbike paddock is a place where I feel completely at home, but there's definitely a big job ahead for the weekend. I don't want to set any unrealistic targets, and I'm not going to Silverstone to re-invent the wheel. I'll just aim to work hard and ride strong all weekend and hopefully get a couple of decent finishes in the races."

Team boss Ronald Ten Kate admitted it wasn't ideal to head into the Silverstone weekend with two substitute riders but said he was confident that both Muggeridge and Lowes - who goes into the weekend on the back of a two-day test at Assen - would do a solid job for the team.

"Going to Silverstone with two replacement riders was definitely not in our plans but of course we wish Ruben a speedy recovery," he said. "We offer Karl a big welcome back to the team after he rode with us way back in 2000 and then from 2003 to 2006, so we have quite a lot of racing history together. He's been doing a great job in the IDM series where he is the reigning champion, so we're looking forward to working with him again.

"Young Alex is starting to gel more and more with the CBR1000RR and two days of testing away from a race weekend was definitely good for all of us. Combining that with a home race for him at Silverstone means we're going to be working flat out to collect more points."