Nico Kuhn had to drop out of the Celtic line-up minutes before kick-off due to an injury niggle.
Brendan Rodgers has confirmed the winger felt an issue "at the top of his thigh".
Kuhn had been listed in the starting XI but was replaced by Yang moments before the Scottish Premiership tie kicked off.
Rodgers explained the matter on Celtic TV after the 2-0 win over Dundee United but admitted the extent of the injury is not yet known.
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"Nothing yet. He felt something at the top of his thigh which was a shame.
"We'll have to see what that is and how that shows up tomorrow."
On BBC Sportsound, Rodgers further added: "Hopefully not [serious].
"He didn't feel he could risk it so we will just need to see."
