The Arsenal defender was impressive again in his side's 3-0 win over Olympiakos on Wednesday.
The Frenchman was part of the side that recorded an impressive 3-0 victory away at Olympiakos on Wednesday evening.
That result was built upon a solid defensive display, with Koscielny and defensive partner Per Mertesacker keeping the Greek hosts at the bay for the majority of the game.
Their performance received plaudits from all angles, and Ferdinand believes that Koscielny is the pick of the bunch when it comes to Premier League defensive talent.
“Koscielny, for me, when he’s on form, he’s the best defender in the league,” he told BT Sport.
“Kompany is not fit or consistent enough. I think this guy, he’s turned into a real top class defender.”
Of all the defenders in the Premier League, there is no denying that Koscielny is up there among the best.
Manchester City’s Vincent Kompany has often been regarded as the best around, but has struggled for form and fitness in recent seasons, as Ferdinand alludes to.
There are other contenders though, Everton and Manchester United defenders John Stones and Chris Smalling have continued to impress, while Liverpool’s Martin Skrtel is also a contender.
Tottenham’s Jan Vertonghen would also stake a claim to the title as well, with him having improved considerably alongside Toby Alderweireld this year.