If you were to look through a list of candidates for Arsenal player of the season last year, it probably wouldn't have taken you very long.
The Gunners slumped to eighth position in the Premier League and failed to qualify for European competition for the first time in a quarter of a century, but one of the few people able to make the disappointing results a bit more palatable was Kieran Tierney.
Either as a left sided centre back in Mikel Arteta's hybrid 3-4-3 at the beginning of the season, or a more traditional marauding left back in the later-adopted 4-2-3-1 the Scottish international's performances were a rare highlight, and there are some within the hierarchy at the Emirates who put their disappointing Europa League semi final exit down to his not being fully fit for those matches.
This campaign though, it has been a different story.
After picking up an ankle injury he was replaced by Nuno Tavares, but found it hard to reclaim his spot in the starting XI due to the Portuguese defender's impressive form and was overlooked for huge fixtures at Anfield and Old Trafford.
Eventually though Tierney did earn his starting spot back at the beginning of December. This coincided with a run of form that has seen Arsenal pick up 25 points from a possible 30 in their last 10 Premier League matches, but still there are some who remain underwhelmed by the former Celtic man's form this season.
So what exactly has gone wrong?
Well, the most obvious place to start feels like the changes in Arsenal's team as a whole.
Last season, particularly before Martin Odegaard and Emile Smith Rowe came into the side, the Gunners' main creative outlet was give it to Tierney and hope.
The Scottish international's delivery was good, but there was no one really in the side to take advantage of this, and watching Granit Xhaka funnel the ball out for him to cross it in to the aerially ineffective Pierre-Emerick Aubameyang and Alexandre Lacazette became like Groundhog Day for the Gunners.
The presence of Bukayo Saka on the left hand side also meant that there was a distinct left sided bias to the way Arsenal attacked their opposition.
This year though things are very different.
With Saka's switch over to the right wing and the presence of Odegaard as the right sided eight in Arteta's subtle 4-3-3, the Gunners' attack is far more diverse in the way it seeks to break down opposing defences.
Given the influence this pair are currently having on the side you could probably even argue that there is a right-sided slant to the Arsenal offence, in contrast to last season.
As a result Tierney's significance in the team has unsurprisingly diminished.
Last season he was averaging 68.8 touches per game which put him up in the 71st percentile for defenders in the Premier League as per fbRef. This time around that has dropped to just 62.1 per 90, meaning he has tumbled to 46th percentile, showing that he is simply just not involved as much in the way Arsenal attack.
More specifically in the last few months though, the role Tierney plays has been forced to change.
The arrival of Takehiro Tomiyasu on transfer deadline day last summer, meant that Arteta finally got the inverted full back he was craving to compliment Tierney's more attack minded tendencies.
The Japanese international is a fantastic defender in transition and provided more cover to Ben White and Gabriel when his opposition fullback looked to go on his typical swashbuckling runs up the pitch.
As Arsenal began to click as an attacking unit around December, Tierney flourished with the increased license to attack, registering a goal and three assists between his return to the side against Everton and the New Year's Day defeat to Manchester City.
Since that loss to Pep Guardiola's side though Tomiyasu has struggled desperately with a string of calf injuries that have seen him make just one appearance in nearly three months.
In that time the former Bologna man has been replaced in the starting line up by Cedric Soares.
The Portuguese international has impressed many with his run of form in the side, but he is stylistically a very different player to Tomiyasu.
Arteta has previously described Cedric as "probably the best (Arsenal) have in the final third to make the right decision and attack the box". In other words his strengths lie more in the attacking side of being a full back than they do in defending in transition.
As a result Tierney has had to alter his game slightly to provide balance to the Gunners when they are in attack, playing a more conservative role than he has done when Tomiyasu is in the side.
This can be seen in his heatmap from Sunday's 3-2 win over Watford, where he spent the majority of his time in his own half while Cedric got forward to play his part in three excellent team goals scored by Saka, Odegaard and Gabriel Martinelli (image from WhoScored.com).
Contrast that to his heatmap from September's win over Tottenham in which Tomiyasu is in the side, and his weighting in terms of attacking and defensive responsibilities is basically a polar opposite (bare in mind the differing directions of play between the two maps).
This shows the difference in the license Tierney has to get forward when Tomiyasu is in the side, compared to when he isn't.
Of course there are certain things in the 24-year-old's game that have been underwhelming.
For example his one-footedness can make him a touch predictable to defend against compared to a more ambidextrous option like Tavares. His pass completion rate is also only in the 56th percentile among defenders in the Premier League this season, suggesting that can sometimes be a bit loose in possession.
But before rushing to destroy Tierney for what he's not doing, it's worth remembering the sacrificial part the Scot is playing for the team right now, and with Tomiyasu unlikely to return for Sunday's clash with Leicester, it's something he could be doing for some time yet.
The former Celtic man might not be at his best, but the fact that he's doing so well in a role that is relatively alien to him deserves plenty of praise. and is perhaps one of the reasons Arteta views him as next in line to the Arsenal captaincy after Alexandre Lacazette.
