Brazilian forward Kaka has added to AC Milan's injury woes after being sidelined with an adductor muscle injury, the Serie A club confirmed Monday.
Kaka, expected to be out for at least two weeks, will now be unavailable for the Rossoneri when they host Celtic in their opening Champions League Group game at the San Siro on Wednesday.
Milan are already without forward Stephan El-Shaarawy, defenders Ignazio Abate and Mattia De Sciglio and midfielder Riccardo Montolivo, all of whom have picked up injuries in recent weeks.
Kaka joined Milan on a free transfer from Real Madrid two weeks ago, having enjoyed huge success with the Italian giants in a six-year spell from 2003-2009.
Despite being included in Massimiliano Allegri's Champions League squad, he will play no part on Wednesday after picking up the injury during a 70-minute spell against Torino on Saturday when Milan scraped a 2-2 draw.
"Muscle damage on the left adductor," said a brief statement from Milan.
"In 10 days the player will undergo further tests to better determine a full prognosis."
Kaka will miss next weekend's Serie A clash against Napoli, Milan's second group game away to Ajax in two weeks time and could also miss the league visit to Juventus on October 6.
The 31-year-old former Ballon d'Or winner, meanwhile, said he won't accept any salary while he is sidelined.
"I've decided to go without pay for the time that I am injured," Kaka said in a video on the club's website www.acmilan.it.
"All I want from Milan is their support so I can heal as quickly as possible."