For close to an hour it looked like the shock of the season was on- St Mirren had taken the lead against Celtic in the Scottish Cup with the hoops toiling to get back on level terms.
Gary Mackay-Steven was replaced by Patrick Roberts at the interval but it took the introduction of Leigh Griffiths after 55 minutes to turn the match Celtic’s way.
Stuart Armstrong dropped into the midfield holding role vacated by Nir Bitton with the former Hibs striker tucking in off Moussa Dembele.
Griffiths won the 58th minute free kick that Roberts crossed in for Mikael Lustig to glance into the net, within a minute some magic from Scott Sinclair put Celtic in front.
Dembele and Griffiths added to the scoreline with two others ‘goals’ being disallowed by referee Steven McLean as Celtic booked their place in the last four of the Scottish Cup where they will meet Sevco in their quest to land the domestic treble.
2 min 20 for Sinclair’s goal.