The 19-year-old is one of Celtic's most important players already.
Despite his age, the 19-year-old is already one of Celtic's most important players after an excellent debut season last term in which he was named Scotland's Young Player of the Year.
The young left-back is certainly a player who manager Brendan Rodgers will be relying on for consistency this season.
O'Connell, who scored in Saturday's 1-1 friendly draw with Leicester City, will be hoping to have a similar impact on Celtic's first team this season, with the 20-year-old admitting that everybody has plenty of respect for young Tierney.
“Everyone looks up to KT. He settled in superbly last year and had a brilliant season," he told The Scottish Sun.
“He is a bit younger than me, but he has set the benchmark with the season he had.
“You can’t really argue with the awards he won and the season he had. What a season it was.”
O'Connell, who spent last season on loan with Cork City, may have been slightly disappointed to see the arrival of veteran centre-back Kolo Toure.
Toure's signing pushes the young Irishman further down the pecking order at Paradise and it remains to be seen whether youngster will be retained by Rodgers this season.
He is also behind Dedryck Boyata, Erik Sviatchenko and Efe Ambrose, although the latter might well leave the club.