Indeed, the French international produced another resolute defensive performance on Wednesday night, despite another European onslaught from the German champions.
The Gunners were up against it from the moment goalkeeper Wojciech Szczesny was sent off for bringing Arjen Robben down in the first half.
David Alaba missed the subsequent penalty but Bayern's numerical advantage meant Arsenal had to defend for their lives. So much so that Pep Guardiola accused the Gunners of having "nine players in the box."
As a result, Koscielny was under a huge amount of pressure. But while questions could be asked of some of his team-mates, his commitment and resilience under that pressure was noteworthy - and may just have saved Arsenal from a humiliating defeat.
The fact that the north London side are only two goals down going into the second leg means they, at least in theory, still have a slender chance of knocking out the Champions League holders. For that, the French defender should take a lot of credit.
Statistics from WhoScored.com show that the 28-year-old made five successful tackles - with two of them being when he was the last man - while also making 10 effective clearances.
Koscielny also blocked three shots and won three offside decisions in Arsenal's favour.
And, although his partner at centre-back Per Mertesacker blocked twice as many attempts at goal, Koscielny made twice as many clearances, one more interception and five more tackles - as the German did not make any.
So if the Gunners do manage to miraculously salvage anything from this tie, then, the Frenchman will be the first man Arsene Wenger should thank.
image: © ronmacphotos