Sonko has been out since January with a knee injury and physio Jon Fearn told the Reading Evening Post: "He has started running and has been doing light power work. He will hopefully start specific football work in August so he will definitely miss the start of the season.
"But in those weeks he will step it up. It will be interesting to see how he copes, but if the carrot could be playing at the end of August - that will be six months after he had the op in February and Michael Owen was out for 11 months with the same injury."
Fearn added: "Marcus won't be ready for pre-season training, but by the time the season starts he could be okay. His progress is slow because he had quite major surgery on his hand."