What Tierney are Celtic getting six years after his exit?

Kieran Tierney is returning to Celtic. After agreeing a pre-contract with his boyhood club, the Arsenal defender will wear his beloved green and white hoops once again.

But away from the romance and hysteria of the Scotland left-back's stunning return in the summer, what player is Brendan Rodgers actually getting six years after his exit to London?

First thing's first, Celtic are getting a hell of a player.

Although he isn't first pick, the fact Mikel Arteta used Tierney against Manchester United and rivals Tottenham last month shows the Arsenal boss feels he is still good enough to play at the very highest level.

In his only start this season, a 3-2 League Cup win over Crystal Palace, Tierney registered 63 touches, completed 38 of his 47 passes, created a chance and won all of his duels.

At his best for the London club, Tierney was one of the top full-backs in a league many regard as the world's best in terms of both quality and drama.

Some Arsenal fans saw the Celtic youth product as a future captain, but he fell out of favour with Arteta after the arrivals of Takehiro Tomiyasu and Oleksandr Zinchenko.

Limited game time meant a season-long loan move to Real Sociedad, where Tierney played 20 times last term as the La Liga side finished sixth in Spain's top flight.

At international level, he has shown he is one of Scotland's most important players. Steve Clarke's team just doesn't function the same without him.

And at 27, his peak years could be on the way. That thought should quite rightly excite the Celtic support.

But a cloud of uncertainly that hangs over is packed with injury worries that have mounted up since his Parkhead exit.

Tierney has only played 108 minutes of football this season after returning from a serious hamstring injury suffered at the Euros in the summer.

Last term he played 1,483 minutes for Sociedad, the equivalent of about 16 full 90-minute matches. The season before was almost exactly the same.

According to Transfermarkt, he has endured 11 spells of absence since leaving Celtic, amounting to 94 games missed for club and country.

That's the equivalent of two-and-a-half seasons of Scottish Premiership football.

It's fair to assume he will be returning to become one of Celtic's top earners, which is of course a risk given his injury record, but a fit-and-firing Tierney undoubtedly improves Rodgers' side at Champions League level.

And that is no slight on Greg Taylor, whose future remains certain with the 27-year-old's contract set to expire at the end of the season.

Taylor, who has won as many Premiership titles as Tierney, continues to be dependable for Celtic, but he has reservations over becoming a rotation player after making himself first-choice left-back.

If he stays, Taylor could ease the load on Tierney if his minutes need to be restricted, giving Rodgers two excellent options.