It’s fair to say that Nicolas Kühn has become something of a talking point among Celtic fans in recent months—and not for the right reasons.

Once a breath of fresh air down the wing, the German winger has seen his form take a worrying dip since the turn of the year, and now even Kris Boyd has weighed in with a cheeky remark.

Boyd said: (Sky Sports), “Maybe somebody should check on Nicolas Kuhn, it looks as if his wisdom teeth have grown back in.”

The joke is a reference to Kühn’s dental issues last year, when he had his wisdom teeth removed shortly after arriving at Celtic. At the time, it was reported that the procedure affected his weight and overall fitness, leading to a noticeable slump in his performances.

Thankfully, Kühn managed to recover well, and in the first half of this season, he looked sensational. Whether it was his electric pace, his clever link-up play, or his confidence to take on defenders, Kühn quickly silenced early doubters and appeared to be fulfilling the potential that seen him once dazzle against RB Leipzig in the Champions League.

But since the New Year, it’s been a different story. His touch has deserted him, his confidence looks drained, and the flair that had Celtic fans off their seats in autumn has all but vanished. There’s no suggestion that dental problems have returned, of course, but Boyd’s joke, as tongue-in-cheek as it was, shows a growing frustration among supporters who can’t quite figure out what’s gone wrong.

To be fair to Kühn, dips in form aren’t uncommon in a player’s first full season at a club the size of Celtic, especially in a position that demands so much physically and mentally. Brendan Rodgers has opted not to single him out in public, but the onus is now on Kühn to rediscover the spark that made him one of the first names on the team sheet earlier in the season.