Tierney rejoined Celtic from Arsenal in 2025. On a tough night at the very start of a new season, against a dogged Dundee, it was a familiar name that helped Celtic usher in victory. No, not Benjamin Nygren - last season's top scorer and the man who nodded in the winner to kickstart the Scottish Premiership defence - but Kieran Tierney, the man who crossed the ball for the Swede to head in.

The left-back has arguably been Celtic's best player since the return of Martin O'Neill in January, but his renaissance has gone a little under the radar. Perhaps that's because we expect so much from the man who once fetched Celtic a reported £25m in a move to Arsenal. Regardless, he still registered 12 assists last season, the most of any Celtic player, and scored six goals from defence.

One of O'Neill's most trusted lieutenants, he's contracted until 2030 but reports have suggested a potential return to Spain, so just how important is he to Celtic? Sportsound: Reaction as Celtic kick-off their title defence with a narrow win over Dundee.

Despite Kasper Hogh's 0.88 expected goals (xG), it was actually Tierney who had the most shots on target for Celtic against Dundee - albeit only two. He created more chances than any of his team-mates (four) and sent in eight crosses, the most of any Celtic player.

"He looked like old Kieran Tierney. He was bombing forward, getting in the box, had a couple shots on goal, doing all his defensive stuff, he was excellent," said BBC Scotland's chief sports writer Tom English. Excellent was the word to describe the left-back's cross to Nygren, and it was just what Celtic needed.

In the first half, the reigning champions were pushed hard by a Dundee side that set out to be aggressive and frustrate the hosts, and that's just what they did. But the chances started to become more frequent, and soon it was the trusty left boot of Tierney that unlocked the door, allowing Nygren to head home from six yards out with a pinpoint cross.

However, his impact on this Celtic team is nothing new. Only Falkirk's Calvin Miller, now at Hearts, registered more assists last season. At Celtic, only Daizen Maeda created more big chances - 14 to Tierney's 12.

Defensively, he consistently shows up as one of the best defenders in the league for his contributions, his tackling, clearances, blocking shots. And for all the talk of managing his minutes, only three full-backs across the league played more than Tierney. That said, he played the full game on only 10 occasions in the league.

"Those players are the football club," manager O'Neill said of Tierney and captain Callum McGregor. "They are the backbone of Celtic, and I'm delighted to have them."

With last season's on-loan left-back Marcelo Sarrachi having returned to his parent club Boca Juniors, there's currently no other senior left-backs on Celtic's books. "Of course [it's important to bring in cover for Tierney], that's something we're looking at," O'Neill told BBC Scotland. "Kieran, with the best will in the world, will not get through every single game. Last year, he was recovering and didn't see some games out because he puts so much into it. We're looking that way."

It was reported today that Osasuna have enquired about Tierney, although that same article suggested Celtic chiefs will knock back any offers for the 29-year-old. Given the lack of options in that position, and also Tierney's importance to the league champions, that is hardly a surprise.

"Kieran's going nowhere, he loves the football club," said his former captain Scott Brown on Sportsound. "You never know what can happen, but I love watching the wee man play, I love his passion. When there's a 50-50 he wins it, when a ball goes into the box he puts his head on it."

"It's the quality on the other side as well. You can see why he went down to Arsenal. Other teams will want that, and Celtic are lucky to have these three [Tierney, McGregor and James Forrest] for that long a period."

Club captain McGregor is another who impressed in the league opener, but there's also been whispers that he might be on the way out. Those rumours seem to have died down in recent weeks.

"Callum has retired from Scotland so he's had the time off, and he looks really fresh," said Brown. "He is the brains of this team, he's got the understanding and leadership. "If any young kids are watching, watch Callum McGregor, watch Kieran Tierney, watch James Forrest. You're not at a football club like this for that long if you can't understand the other side of the game."

This video cannot be played 'I hope he's here until he's 45!' - O'Neill hopes McGregor is staying at Celtic.