World champion Casey Stoner on Friday told long-time rival Valentino Rossi to mount a serious challenge to his crown after a lacklustre season left the Italian without a race win for the first time in his 15-year career. Australian rider Stoner, the 2007 and 2011 champion, wants to see a healthy challenge launched by Rossi\'s Ducati team, but doubts their potential to eclipse his Honda outfit. \"They are saying that they completely revamped 90 percent of the bike, but they did that in the middle of last year. They changed the bike back to front and top to bottom and nothing much changed,\" said Stoner. \"I’m hoping, for Ducati’s sake, that they can put together a competitive bike this year because the championship needs it. \"Regardless of what the riders want, everyone needs as many manufacturers at the front as possible. Yamaha and Honda want competition; unfortunately Kawasaki and Suzuki are gone from the championship, so we need all bikes at the front.\" Stoner won 10 races in 2011 and believes that once again it will be Yamaha\'s Jorge Lorenzo, the 2010 world champion, who will be his main rival when the new campaign gets under way in Qatar on April 8. \"Jorge was first in 2010 and second in 2011, he will always be there fighting. All the factory guys as well as Andrea (Dovizioso) will be pushing up there on the Tech 3 Yamaha, it’s the same crew as in the past,\" Stoner told www.motogp.com. Before the season starts, however, Stoner has a more pressing concern as his wife Adriana is expecting a baby. \"Adriana is doing great. We just want these last few weeks to go as smooth as possible. I hope I can be home for the birth as it’s due right in the middle of both tests, so I’m crossing my fingers I can be home for it.\"