The Arsenal manager handed the big German his first start since the beginning of January as the Gunners headed to the City Ground to take on Nottingham Forest in a FA Cup third round tie.
But it didn’t quite work out as Forest put them to the sword in a shock 4-2 victory.
There were several disappointing performers in the Arsenal team, but you’d be hard pushed to find any as poor as Rob Holding and centre back partner Mertesacker.
Keown was a commanding presence in defence for Arsene Wenger during his career so he’s well placed to analyse the current crop of defenders at the club.
And it’s safe to say he’s not impressed with Mertesacker, insisting he could retire today rather than waiting until the end of the season:
"He may have actually retried Mertesacker today…" ?
Martin Keown thinks the Arsenal defender was exposed against the Nott'm Forest youngster, Ben Brereton. pic.twitter.com/PAJqLq8Pti
— Football on BT Sport (@btsportfootball) January 7, 2018
Mertesacker has played less and less over recent seasons, but Wenger continues to bring him in on occasion and today’s performance and result suggests that’s not a good idea.