The 24-year-old was delighted with the Bhoys' 4-0 win over Aberdeen.
It was only 1-0 at half-time, though, and Mackay-Steven admits it was a scrappy first half. The Hoops were never worried, however, the 24-year-old says...
GMS: "It was a scrappy 1st half, not too much football was being played. We got the goal and always good to go in at half-time 1-0 up." (MH)— Celtic Football Club (@celticfc) March 1, 2015
GMS: "We knew if we got the ball down & played in the 2nd half, gaps would open up and we would exploit that - that's what happened." (MH)— Celtic Football Club (@celticfc) March 1, 2015
The victory leaves Celtic six points clear of Aberdeen with a game in hand over the Dons.
And such is the Bhoys' commanding position now, Mackay-Steven is naturally delighted with the situation Celtic have left themselves in.
A domestic treble is very much on the cards for Ronny Deila's side and the 24-year-old winger is pleased with the winning mentality the Hoops have acquired.
GMS: "It was very pleasing. Today was a massive game for us. Aberdeen have been pushing hard and important to get the win." (MH)— Celtic Football Club (@celticfc) March 1, 2015
GMS: "If we win on Wed. we will be nine points clear so a big win for us." (MH)— Celtic Football Club (@celticfc) March 1, 2015
GMS: "The club is used to winning and there is a definite winning mentality in the dressing room - second best is no use." (MH)— Celtic Football Club (@celticfc) March 1, 2015
Up next for Celtic are St Johnstone in the Scottish Premiership on Wednesday night, where, as Mackay-Steven says, the Bhoys could extend their lead over Aberdeen to nine points.
What a result they secured against the Dons - and what a position it's left them in.