The former Arsenal central defender and manager has been impressed with the performances of Tierney.
Neill has also praised the Scotland international defender for his attitude, and how he comes across in interviews.
Neill told The Sunday Post about Tierney: “It’s obviously still early days with Kieran but, from what I’ve seen so far, I’ve been immensely impressed.
“Let’s not forget that Kieran is still only 23, and he’s not nearly as good yet as he’s going to be. Every time I see him play, he looks better than the time before, so there’s even more to come from him.
“But it’s not just his performances that I’ve been taken by. Football, and life, is about more than just the odd flash of talent, and when I hear Kieran being interviewed on television, he seems such a grounded individual. His mental strength stands out as well, so he was clearly well-schooled at Celtic.”
Tierney joined Arsenal from Scottish Premiership giants Celtic in the summer of 2019 for a transfer fee reported by Sky Sports to be worth £25 million.
The 23-year-old arrived at the Emirates Stadium with a strong reputation, having won the Scottish Premiership title four times, the Scottish Cup twice and the Scottish League Cup on two occasions with the Hoops.
The left-back struggled with fitness and injury problems initially at the Gunners, but he has been superb since football resumed after lockdown.
According to WhoScored, Tierney made 12 starts and three substitute appearances in the Premier League for Arsenal this season, scoring one goal and providing one assist in the process.
The left-back also provided two assists in four Europa League matches for the North London outfit this campaign, according to WhoScored.