By all accounts, Calum Chambers' move from Arsenal to Aston Villa has taken many by surprise.
On Thursday night it was announced that after seven-and-a-half years, the versatile defender's time at the Emirates Stadium came to an end with him joining Steven Gerrard's side for an undisclosed fee.
"Calum Chambers has joined Aston Villa in a permanent transfer for an undisclosed fee," a statement read on Arsenal's official website. "Joining us from Southampton in July 2014 as a 19-year-old, Calum soon became a full England international, having previously starred for the Under-21s.
"The defender made 122 appearances in all competitions during his time with us, winning both the FA Community Shield on his debut in August 2014 and the Emirates FA Cup in 2015.
"We wish Calum all the best for the next chapter in his career and thank him for his contribution to Arsenal over the past eight seasons.
"The transfer is subject to the completion of regulatory processes."
Chambers becomes the 10th Arsenal player to depart this month and is the second permanent departure from the first-team following Sead Kolasinac's move to Ligue 1 outfit Marseille.
Furthermore, the 27-year-old is the fourth senior central defender to have left the club at some point this season.
With William Saliba, Konstantinos Mavropanos and Pablo Mari on loan at Marseille, Stuttgart and Udinese respectively, it means Mikel Arteta's options at the heart of defence are limited.
Whilst Chambers has barely featured this season, he did provide cover at right-back, central midfield and would have been the fourth-choice central defender behind Gabriel Magalhaes, Benjamin White and Rob Holding for the remainder of the campaign.
Now, it's possible that Arsenal will be able to get through the season with three centre-backs especially as they're out of both domestic competitions and not in Europe.
But if something was to happen to one of Gabriel, White or Holding it would pose a problem.
In Takehiro Tomiyasu, Arteta has a player who does operate as a central defender for the Japan national team and that might have been the Spaniard's thinking behind letting Chambers and Mari leave this month.
Although, the drop in quality when the 23-year-old isn't in his natural role at right-back proves it would be a risky call.
Alternatively, Arteta could look to promote from within the Under-23s setup.
The one name that immediately jumps out is Omar Rekik, who arrived from Hertha Berlin last January. He made his senior debut in a pre-season friendly against Hibernian and has often trained with the first-team.
Furthermore, the 20-year-old has been capped three times at international level and is currently with Tunisia at the Africa Cup of Nations ahead of their quarter-final against Burkina Faso.
Yet to be included in an Arsenal matchday squad for a senior game, could the exits of Mari and Chambers lead to a first-team promotion for Rekik with him as the fourth-choice centre-back for the remainder of the season?
Well, in the defender's own words, he would have no problem playing alongside one of Gabriel, White or Holding if called upon.
"My style of play? I’m a central defender and I like to play with the ball, I like to play out from the back, and I think this is also the structure of the club," he told Arsenal.com. "It fits perfectly."
Interestingly when Rekik was unveiled as an Arsenal player, he was described as a "ball playing centre half who can play on both sides".
With Mari gone, there's no natural left-footer as cover for Gabriel so the fact the 20-year-old is comfortable on the left-side might increase his chances of being called up in case of an emergency.
In addition, Rekik is able to operate at right back and in defensive midfield - the latter an area where Arsenal are looking to strengthen this month - so the Tunisian could end up saving the club a few million pounds in the January transfer window.
