It is hard to pinpoint any one issue, but the turnover of players is something often overlooked.
Twenty-four players have arrived in the three windows under Thelin, with plenty also heading in the other direction.
In January Aberdeen effectively signed a brand-new defence, and then had to replace left-back Jack Mackenzie this summer too.
Last season’s first-choice goalkeeper Dimitar Mitov missed long spells with injury.
When they won 13 straight games, the Bulgarian started behind the same back four for virtually all of them.
But it is not just a lack of continuity at the back which may have contributed to poor defending, but an apparent lack of physicality and aggression at times.
Aberdeen have lost more challenges, according to Opta data, than any side in the Premiership since the start of last season.
That could also be down to players not reacting quickly enough, or being in the right positions, but either way it is a concerning statistic in a league like the Premiership, where winning tackles and second balls are vital.
A lack of continuity may also be holding back the attack. Of Aberdeen’s forwards, only Topi Keskinen (35) has started more than 22 of their last 41 league matches.
Jamie McGrath, Pape Gueye, and Shayden Morris were key creators and scorers for Thelin last term and have now left the club.
Overall, only Celtic and Rangers have made more line-up changes than Aberdeen.
The club have created a successful player trading model since chairman Dave Cormack took over stewardship of the club in November 2019.
That means looking for value from younger players playing in some of Europe’s less-heralded leagues. With that comes risk, and plenty of those who have arrived are yet to prove themselves.
Keskinen, 22, is a good example. Signed for a healthy fee from HJK Helsinki, the winger has had bright moments, but has only produced two league assists and five goals in 39 games.
Under a manager who sees his wingers as key to his system, that return is not enough.
However, Keskinen is far from the only culprit.
“Jimmy Thelin’s got a lot to think about,” former Aberdeen captain Willie Miller said on Sportsound after the Falkirk game.
“He’s brought a lot of project players in and, as yet, we’ve still got to see the fruits.
“There are so many new players coming in and it’s a very young squad as well. There are a lot of them 23 and under. They don’t have a great deal of experience.
“All these players need to convince that they are good enough for the club.”
