Here are the opinions of some of Casey Stoner's former rivals, plus new boss Gigi Dall'Igna, after the Australian's impressive MotoGP return as a Ducati test rider at Sepang.

The 30-year-old double world champion, who retired at the end of 2012, set the fifth best lap time on the final day of official testing and was also the fastest Desmosedici rider.

Jorge Lorenzo: "First Ducati rider - not bad after several years fishing! Obviously this track he likes, it is one of the favourites for Casey, but Iannone is not slow. He is one of the fastest riders and he is behind. Andrea [Dovizioso] also has a lot of experience and likes Sepang and is behind also. So it demonstrates that Casey didn't lose the talent and speed."

Valentino Rossi: "First of all, it is very good to see the lap times like this [on the timing screen]; Lorenzo, Rossi, Marquez, Stoner, Pedrosa - everybody. This is very good for the championship. Already the level is very high but with Stoner he has more potential that can come, but he was very fast. I think he wants to race but I don't know if it will happen." [Stoner denies he plans to race].

Cal Crutchlow: "Casey is Casey. He is an incredible rider and probably the fastest of the last decade, give or take. He and Marc are the two guys you'd look at for sheer speed. I didn't expect him to be any less fast than he was.

"He knows how to ride a motorcycle. Sure, having a year off is not easy. I wouldn't want to come back and be thrown in the deep end, but for sure he's an incredible rider. In my eyes it wasn't going to be anything different. He wasn't going to be doing 2m 7s.

"He's ridden motorcycles all his life and he's natural at it. I didn't expect anything less. He's certainly shown everyone that his speed is still there, no doubt about that, imagine if he did another three or four tests and a race. He's going to be there. I can guarantee that. It was good to see him back."

Gigi Dall'Igna (Ducati): "It's really easy [working with Casey]. His feedback is really good since the first day. We prepared some test list for the first day but frankly speaking I didn't expect him to do anything; just try to work on the set-up and to give him the right feeling on the bike.

"At the end of the first day we finish completely the test list and this surprised me. I didn't expect this. He's confident with the bike and the tyres. This is only his third day with the bike...

"Frankly speaking I expected this [speed] from Casey. He is fast. This is not strange news!"