Hearts goalkeeper Craig Gordon hailed the performance of the left-back.
"I thought he was incredible - and he has taken his game on even further," said the veteran. "He talks so highly of the Arsenal coaching staff and how they have helped develop him.
"For us, over the last three games he has been excellent - if not the standout in every single one.
"He has been magnificent and hopefully we can keep him fit and playing at this level.
"I think he is world class, I really do. He is so consistent as well and that is what makes him so good.
"He is doing it in every game and he's a big asset for us on and off the park.
"He is also in charge of the music and he is great for the camp, a real valued member of the squad."
Explaining a little more detail on the improvement in Tierney since his 2019 move to London, Gordon said: "He has been more consistent.
"Tactically and technically he has improved, playing against better players week in week out. He has raised his level because of that.
"I have seen him come through from 17 to where he is now - and he will only continue to get better."