When the reckoning comes for top-level defenders it is swift and often brutal. For players who have spent their careers further forward the tendency is to drop back, but if you do that as a defender you find yourself off the pitch entirely. That might be happening sooner than expected for Kyle Walker, the unfortunate embodiment of Manchester City’s sudden downturn.

Pep Guardiola has extracted superheroic levels of performance and consistency from his squad and few have been as important as Walker, who arrived a year into the Spaniard’s reign and immediately won a League Cup and title. That was seven seasons ago, when David de Gea was the best goalkeeper in the league and Mark Hughes was still a top-flight manager. A different era, and it is remarkable Walker has not only lasted but thrived in this new one. But there is no place to hide in his position.

Frequently exposed and shown up by the nature of their work, the current Premier League is a merciless environment for an ageing full-back. The past few weeks have generated more hairy moments for Walker than the previous few seasons. None of this was helped by his behaviour in Sunday’s Manchester derby.

‘Embarrassing’ clash in Manchester derby

Shortly after Manchester City had taken the lead Walker barged over a running Rasmus Hojlund, then the Manchester United forward squared up to Walker in the established style to avoid punishment: foreheads coming together with minimal force. After a second or two of mutual verbals Walker decided it was time to throw himself to the ground as if he had entered a Looney Tunes cartoon and just been hit by an Acme anvil falling from the sky. “I don’t know the guy and I am embarrassed for him,” said voice of the nation Roy Keane.

BBC podcast may need a rethink

Please prepare to clutch some nearby pearls, but such gamesmanship is hardly a rare sight in the Premier League and would not be enough on its own to suggest any wider strife for Walker. Yet there has been plenty of other evidence during his recent matches. You’ll Never Beat Kyle Walker is the name of the defender’s BBC podcast. It may have to be revised.

Exposed by Werner

He has managed to tick every box on the list of reasons for City’s current decline. His once fearsome pace looks diminished, an example of the club failing to renew sufficiently as stalwarts of their team age. At times he appears either unable or reluctant to put in the running necessary, most obviously at home to Tottenham when Timo Werner breezed past him to make Brennan Johnson’s goal, Spurs’ fourth. Walker looked slow to react to the threat as it developed then could not find the required higher gear to compensate.

... and Traore

See also Adama Traore, admittedly one of the quickest in the league, comfortably winning a foot race against him during Fulham’s 3-2 defeat by City in October. These are the sorts of situations Walker has rescued himself from hundreds of times in his career, now he is playing without the safety net of extreme speed summonable at will.

Mental lapses

There have been mental lapses too, like playing Daniel Muñoz onside for Crystal Palace’s opening goal at Selhurst Park last weekend, then seemingly forgetting to jump as Maxence Lacroix sprung above him to head Palace’s second in from a corner.

Walker has had a career of remarkable longevity, with few modern parallels beyond Ashley Cole in his position. Unfortunately it is another Premier League all-time all-star Gary Neville who comes to mind currently, specifically his disastrous final few games for United which led to a snap mid-season retirement in 2011.

No need for that with Walker, who does not have Neville’s temptation to finish neatly as a one-club man. He has proved himself capable of adapting, may benefit from a rest and would still improve most Premier League teams. But football is cruel. His time of elite dependability could finally be nearing its end.