Arsenal midfielder Mathieu Flamini was notable by his absence in last night's Champions League humbling, at the hands of last year's finalists, Borussia Dortmund.
The 2-1 defeat will have provided Arsene Wenger with plenty of reason to be optimistic about his side's chances of success in 2013/14, but the lack of defensive cover in front of his back four, must be a slight cause for concern.
Flamini's return to north London was met with a mixed reaction from Gunners fans; some determining his free transfer capture an underwhelming signing, others a sensible piece of business by the notoriously frugal French tactician.
However, even the most ardent of Flamini supporters could not have predicted just how important a role he would play in the opening period of the season, that has seen Arsenal ascend to the top of the Premier League table.
Since making his second debut against Tottenham in the north London derby victory in August, last night was the first game outside of the Capital One Cup that the 29-year-old has missed, since leaving AC Milan to return to the Emirates Stadium this summer.
Most of the headlines have centred around the club-record signing of Mesut Ozil, or the imperious form of Aaron Ramsey, but Flamini has gone quietly about his business, doing all the 'dirty work' to allow the rest of Arsenal's attacking midfield unit flourish.
His big-game experience and vocal presence in a young Gunners side has also proven invaluable in recent weeks, while his disciplined displays in front of the back line, have helped shore up what was at times a leaky defence last season, and released the shackles to enable the likes of Jack Wilshere, Santi Cazorla, Ozil and Ramsey to operate at their counter-attacking best.
After Flamini was withdrawn midway through Arsenal's 4-1 victory over Norwich City last Saturday with suspected concussion, Wenger now finds himself without a like-for-like replacement for the dependable defensive midfielder.
With him in the team last night, the Gunners might well have got the better of Borussia Dortmund, and not been undone by the direct run of Kevin Grosskreutz and deadly finish from Robert Lewandowski that sealed victory for the Bundesliga giants.
The sooner Flamini returns to fitness, the better. Arsenal need the reliable midfield enforcer if they are to have any chance of challenging on both domestic and European fronts this season.