The Swiss defender spent two years with the Hoops following his move from Manchester United’s youth team in 2015.
But he played just 20 times under Ronny Deila and Brendan Rodgers before spending a short time on loan at Barnsley and eventually getting a permanent switch away to Ligue 1.
At Celtic, he was very suspect as a right back and that was shown on numerous occasions and, despite showing more promise going forward, it was no surprise when Rodgers moved him on.
Yet a year on from now, Janko is being linked with a move to Porto after making 22 appearances in his debut season in France.
According to L’Equipe, per ojogo.pt, Janko is is seriously interesting the Portuguese champions – and that would be a huge move for him if it were to go ahead.
Porto won the Primeira Liga last season while getting to semi-finals in both domestic competitions and the last 16 of the Champions League.
So Janko could look forward to challenging on all fronts if he becomes a Porto player over the coming week.