The match finished with a controversial moment when Leigh Griffiths felt he should have had a penalty after a challenge from Clint Hill.
Hill knew he was lucky to get away with it, as it would likely have resulted in a second yellow card for the defender too, and he admitted to Hoops manager Brendan Rodgers that it was indeed a foul. "It looked a clear penalty", Rodgers said.
"I saw the start of the game and St Mirren did well, but I think Celtic were comfortable in the end".
That may have irked the Dons, who are Celtic's closest challengers in the Scottish Premiership.
"I was much happier with the second half".
The 20-year-old has been at the centre of a lot of transfer speculation, with Barcelona rumoured to have gone to watch him when they were about to face Celtic in the Champions League group stage. We weren't so good in the first half.
Both the teams will stop at nothing to pick up three points. We were passing backwards and sideways instead of forwards.
"It's a hard environment, but two outstanding saves from Craig Gordon or it could have been more".
"We aim to win every game".
Rodgers described Armstrong's performance as "excellent" and acknowledged the team lost "a little bit of control in the middle of the pitch" after the midfielder was substituted due to a tight calf.
"I've just said to the players that I'm incredibly proud of the way they've worked and the way they've accepted me", he said. "Craig Gordon made two magnificent saves; I thought we deserved that goal", Murty told Sky Sports.
"When you concede late on it feels like a loss, but, in the next couple of days, we will realise we have kept our run going and we are still unbeaten".