Nicolas Kühn has been tremendous at certain points for Celtic this season…

The German winger struggled when he first arrived last January but that was explained in a tell-tale interview with the player, regarding health issues that had been plaguing him when he first joined the Scottish Champions.
Dental problems at the start of Kuhn’s time at Celtic
Nicolas had to have his wisdom tooth removed and it had subsequently had a knock on effect, as he lost considerable weight and looked jaded whenever he was on the field of play. That first six months was all about building himself back up again to his former powers, just like when he was playing for Rapid Vienna in the Austrian first division, where Celtic set their sights on him for a winter transfer window move.

Kuhn started this season brilliantly
With that behind him, the wide man started this season on fire as he began to really show everyone just how good a talent he was, and likewise, how good he could be with the right development and career trajectory. His goals tally and assists were something to behold as he started to really rack them up in spectacular fashion, which included in the Champions League.
His latest display in the Glasgow Derby match was so insipid and weak
Since the New Year though, Nicolas Kuhn has gone off the boil somewhat and has endured a dip in form, with only really that goal against Bayern Munich in the Allianz Arena being noteworthy. His latest display in the Glasgow Derby match was so insipid and weak, that Brendan Rodgers removed the player at half-time in what was a clear message to him.

Hartson reckons Kuhn has been over trying at times
John Hartson reckons that Kühn needs to get back to his best again and insisted he must stop trying too hard for this to happen. Speaking to the Go Radio Football Show, the former Celtic star said: “For me, Kuhn has been excellent all season but in the last three or four games he has been over trying at times.

“When it is not on to beat the player, you have to come back inside and look to go out the other side. Wait until you are in that position where you are one on one and can drive at the full back.
“I don’t know the particular reason for it, but he needs to get back on it because Celtic still have a lot to play for this season.”
Paul Gillespie

Think John is being kind here, I thought he couldn’t be arsed trying
the goal against Bayern yet losing the tie overall probably dented his confidence, and maybe he is thinking of a move away in the summer?
on the other hand, I’d start Yang more now