What did we learn from Tierney's Celtic return?

Tierney rejoined Celtic from Arsenal this summer

Celtic fans can breathe a sigh of relief knowing that Kieran Tierney's substitution during his first game for the club after six years away is nothing to worry about.

The 28-year-old's withdrawal just after the hour of the opening-day victory over St Mirren was merely to "manage" the left-back and not a sign of anything more serious, manager Brendan Rodgers confirmed.

Given the left-back's horror run of injuries since leaving Glasgow, the supporters' angst was understandable.

Tierney returned to Scotland this summer following the expiration of his Arsenal contract and will want to prove to supporters that he is as good as when he left.

His first competitive game back showed glimpses that he is, but what did we learn from the Scotland defender's first game back?

Celtic must 'manage' Tierney's fitness

There was a collective groan from the stands when Tierney went down just after an hour into this stodgy win.

Worries from the latter stages of his first spell, and much of his time with Arsenal, about his fitness crept into the collective consciousness of Celtic fans.

In the final season of his last spell in Glasgow, Tierney started 19 league games and missed a large chunk of the season with a hip injury before heading to Arsenal, where he had an equally troublesome time with his fitness.

Last season, Tierney played fewer than 500 competitive minutes across 20 games, having missed the first three months of the season with a hamstring injury sustained while playing at the Euros for Scotland.

But having been taken off during the first competitive start of his second spell at Celtic, Rodgers assured supporters the substitution was purely precautionary.

"He's still building his fitness," Rodgers told BBC Scotland. "He hasn't played a lot of football in the last few years so we have to manage him."

He still offers attacking threat

Celtic fans will fondly remember the danger Tierney posed bolting down the left-hand side during his first spell.

Although he only scored eight goals in 171 appearances last time around, he set up 37 and played a large part in creating many more.

Those at Celtic Park on Sunday were treated to glimpses of that once again.

Only Adam Idah bettered Tierney's two shots, and his 16 final-third entries were eclipsed only by fellow full-back Alistair Johnston - likewise his 30 passes into the final third.

Liam Scales and Callum McGregor - who both played 90 minutes - were the only two players to complete more passes. And Tierney also won possession six times.

Left-back slotted straight back in

While many new signings can look a little hesistant on their debut - particularly among the noise of Parkhead - Tierney looked like he had never left.

The defender slotted seamlessly into the backline and played with the calmness and confidence many supporters will remember from his first spell in Glasgow.

"Kieran looked very, very good," manager Rodgers told BBC Scotland.

"Once he understands a wee bit more how we play he'll be able to get into positions that fraction quicker.

"Overall it was fantastic to see him back at Celtic Park."