Bolton defender Ricardo Gardner will miss the start of the season after tearing his hamstring.
Gardner will miss the start of the season on 11 August
The 28-year-old was carried off after coming on as a second-half substitute in Thursday's Peace Cup draw with Seongnam Ilhwa in Seoul.
The Jamaica international is set to be out for six weeks.
Meanwhile, Stelios has returned to training after a calf injury, while tournament organisers nullified Nicky Hunt's red card against Seongnam.
Bolton instead paid a £500 fine, which will be donated to youth football projects in Korea.
Stelios was ruled out of Thursday's match but Bolton boss Sammy Lee told the club website: "The injury to Stelios is not as bad as first feared.
"The medical team will monitor his rehabilitation over the next few days with a view to him resuming training at some stage early next week."