The 22-year-old felt the 'amazing' events of Thursday night were a great credit to his team-mate.
The Celtic winger got the Hoops back into the game with their first goal before then playing his part in the equaliser that leveled things at 2-2 (it finished 3-3).
Mackay-Steven feels the second goal should also go down as the 24-year-old's and he was delighted his fellow Celtic newbie could claw the Scottish champions back into the tie.
“I think you’d have to credit him with the two goals,” Mackay-Steven said. “It was amazing. Adam Matthews got to the byline and put a great ball in to find Stu with a great finish.
“He was there again for the second one as well so it was great for us. We needed that and from then on the crowd were the 12th man and they really spurred us on for the rest of the game."
Celtic host Hamilton Academical this Sunday afternoon looking to cement their position at the top of the Scottish Premiership.
Then, all focus will shift to the return leg at Inter Milan. Roberto Mancini's men will have the plus that they netted three away goals in Scotland - but the Bhoys will know they came back from the dead to keep their European hopes alive.
More of the same from Mackay-Steven and Armstrong, meanwhile, will no doubt be more than welcome for boss Ronny Deila.