Aston Villa star McGinn scored a late equaliser with a spectacular bicycle kick.
Speaking after the game, Arsenal left-back Tierney said: "Your heads can drop, you can stop being negative but we stuck to what the manager told us to do and we got the rewards.
"And it was a great finish as well. It was unbelievable, eh?
"He's been practicing that on FIFA all week so he has.
"It's probably a fair result in the end, two good teams going at it.
"We lacked belief at the start, but when we started to believe we knew we could hurt them, we knew we could get goals and coming back twice against a team like that is great character.
"It was a positive result, we've got two more games this week coming up and we'll be looking to get more points."