The 34-year-old departed the Premier League outfit for Shanghai Shenhua in the summer, but returned to watch his old side in action on Sunday.
The Chinese season is now over, but the Ivorian will continue training in a bid to keep fit for the African Cup of Nations, which will begin in January.
"He's a legend at this club, a real pleasure to work with. If he needs any help from us, he'll always be very welcome in our club," Di Matteo told reporters.
Drogba has been linked with a return to the Premier League in recent weeks.