Valentino Rossi will face his first home Italian Grand Prix as a Ducati rider without crew chief Jerry Burgess this weekend.
A statement from Ducati explained that Burgess - the most successful crew chief in motorcycle grand prix history and at Rossi's side ever since his 2000 MotoGP debut - "has returned to Australia to be with his wife, who must undergo a series of medical exams and a possible urgent surgical procedure."
Burgess, who has won world titles with Rossi (7), Mick Doohan (5) and Wayne Gardner (1), is expected to be back for the following German Grand Prix at Sachsenring.
“First of all I'd like to wish good luck to Jeremy, who won't be able to join us this weekend due to very important personal reasons," said Rossi. "We'll miss him very much in the garage, but we look forward to seeing him at the Sachsenring."
At Mugello, the role of Rossi's crew chief will be filled by Max Bartolini, who normally works as the team's Technical Manager.
That place will in turn be filled by Fabiano Sterlacchini, who is usually the Technical Manager and Track Engineer for Pramac Ducati's Loris Capirossi, who will miss his home race due to injuries at Assen last weekend.
“We're very sorry not to have Jeremy with us at Mugello for our home race, where we'll have many fans in the grandstands," said Ducati team manager Vittoriano Guareschi. "We're with him in spirit, and we're awaiting his prompt return.
"In the meantime, we've revised the working structure in the box with the addition of Fabiano Sterlacchini, a very experienced Ducati engineer who normally looks after Loris, who is unfortunately injured.
"We thank Paolo Campinoti and the Pramac Team for making Fabiano available to us so that we can fully support Valentino for a very important race."
Rossi broke his leg in practice for last year's Mugello round, but had previously won his home event on no less than nine occasions.
The Italian has taken just one podium finish so far this year, although he holds fourth in the world championship.
The Italian Grand Prix will be Rossi's second race with the GP11.1 motorcycle, which combines the 2012 Ducati chassis with a new seamless-shift gearbox and an 800cc engine.