Celtic striker Oh Hyeon-Gyu could be sidelined for up to six weeks with a calf injury.

The 22-year-old South Korea international suffered the original problem playing in James Forrest's testimonial match against Athletic Bilbao but did not reveal the injury before taking his place on the bench for champions Celtic's Scottish Premiership opener against Ross County at Parkhead on Saturday.

"Oh will probably be out for a few weeks," Hoops manager Brendan Rodgers said Wednesday.

"He hurt his calf against Athletic Bilbao but no one knew and he trained on.

"He was involved in the game at the weekend and then he trained on the Sunday and afterwards he spoke to the medical team to say he felt his calf and it has ended up that he has a calf problem which might put him out for four to six weeks. So that's where he is at."

Rodgers added: "Apart from that, the injured guys are doing really well.

"Ali Johnston is back on the grass, running, working, he is increasing his intensity so that is really good news for us.

"Marco Tilio is also now out on the grass and moving well so we expect him to be another month or so away."