Strength in depth wins the day for Brendan Rodgers' Celtic
Brendan Rodgers exploited Celtic's strength in depth as the Hoops came from behind to beat St Mirren 4-1 in their William Hill Scottish Cup quarter-final.
Harry Davis fired the Ladbrokes Championship side into a shock early lead as Celtic struggled to get going in the first half.
Rodgers brought on Patrick Roberts for the ineffective Gary Mackay-Steven at the break and striker Leigh Griffiths then replaced Nir Bitton in the 54th minute.
Quickfire goals from right-back Mikael Lustig and attacker Scott Sinclair turned the game around for the home team before striker Moussa Dembele and Griffiths made the victory more emphatic.
The runaway Premiership leaders were later drawn against Old Firm rivals Rangers in a Hampden Park semi-final, with Aberdeen taking on Championship leaders Hibernian in the other tie.
Rodgers spoke about the spark provided by Roberts and Griffiths, who were joined later on by January signing Kouassi Eboue, making his debut off the bench.
He said: "I felt the game needed that. I know what they can do.
"I don't need food for thought - I know what their qualities are and I know what they bring to a game.
"Hence why sometimes we use them and sometimes we don't.
"I think what is clear is that I have a very strong squad capable of scoring goals, creating chances and in the main defending very well.
"I thought young Gary worked very hard but he could have been playing for the next 10 hours... sometimes you get games like that as a player where it's just not going to go right for you.
"You have a choice as a manager. You either keep him on and see if it changes or you have a decision to make. Do you make the change?
"I thanked him because he had worked so hard but it's just not your day.
"When you have able people on the side to freshen things up like young Pat, who is an outstanding talent, then he can come in and see if it is his day.
"It ended up he came in and we had the plan that if it wasn't going the way we wanted it to go after 15 minutes then we had Leigh on the bench who can add goals and give another threat to them.
"It worked out quite well for us in the second half."