Joe Hart has just discovered what an unforgiving business elite football is. Less than 18 months after being crowned a Premier League champion he is dropped for Costel Pantilimon for Manchester City's match with Norwich City, with his place as the England No1 in this World Cup year now seriously threatened.

Hart faces a long road. Goalkeepers are not generally rested as any outfield footballer might be, and are always reluctantly dropped. In deciding whether to back or discard a player who has become a liability, the manager must consider how much an already fragile confidence will be affected by either choice.

Stay with Hart, as Manuel Pellegrini, the City manager, had done despite the catalogue of mistakes already recorded this season, and the risk was that a further howler might do irreparable damage.

Stand him down, as he has now done, and the spotlight further intensifies in the Chilean's official confirmation that Hart is no longer the pair of safe hands he once was.

Scott Carson, Paul Robinson and Robert Green offer three recent illustrations of how a goalkeeper's lot can fall dramatically from the upward trajectory to a battle to avoid career disintegration. All three made critical errors when on England duty, and Roy Hodgson will again face questions regarding whether he should retain Hart as he prepares the side for the friendlies with Chile and Germany in a fortnight.

With Fraser Forster, John Ruddy and Ben Foster unproven at international level, Hodgson's judgment could go right to the heart of how England will fare in Brazil at the World Cup.

Ray Clemence, the former England, Liverpool and Tottenham Hotspur No1, is aware of the jeopardy to his long-term prospects Hart now encounters. "What we have to be careful of – and we are terrible for it in this country – is getting on somebody's back and destroying their confidence," Clemence told TalkSport. "I've seen it happen to Paul Robinson when that ball bounced over his foot [playing for England] in Croatia, and Scott Carson was never forgiven for the Croatia game at Wembley [where defeat cost England a place at Euro 2008]. It just affects them and some don't recover from it. I don't want to see that happen to Joe. He's a wonderful lad, a great character and he has got a strong personality."

On the question of whether Hodgson may follow Pellegrini and replace Hart for England, Clemence says: "Joe Hart is the best goalkeeper England have got at this moment, but he is going through a difficult time, and I'm pretty sure he would be the first to admit that. We all go through bad times and you need people to stand by you and have confidence in you."

Yet Pellegrini steps forward as the manager who has lost that faith in Hart. The narrative established last season of an erratic Hart has continued as Pellegrini witnessed errors at Cardiff in the 3-2 loss in August, two more mistakes in Bayern Munich's 3–1 win in the Champions League last month, and the one at Stamford Bridge on Sunday that has finally cost the keeper his place.

The mistake Hart fashioned that allowed Fernando Torres to score in the dying moments to take all three points for Chelsea moved Pellegrini to decide that for the sake of City's tilt at reclaiming the title – and his own job prospects as manager – the axe should fall.

Pantilimon, who has been City's go-to option in cup competitions, has never played in the Premier League, which further underlines the major call the manager has made.

But with the Romanian having decided that if not selected against Norwich he would consider his future in readiness ahead of the January transfer window – a scenario Pellegrini is aware of – the manager's hand was further forced.

How the 26-year-old fares against Chris Hughton's side will fascinate, with Pantilimon often identified as not being able to provide stiff enough competition for Hart.

Clemence says: "It's good to have somebody that makes you think: 'If I make a mistake here, I'm under pressure and I might not be in the team next time.' Intense competition does keep you on your toes. At Liverpool, they used to change the reserve goalkeeper every three years to make sure I had a new challenger, so I didn't get complacent."

On the question of Hart's international spot, serious rivals are also vital, Clemence adds: "It does help, without a shadow of a doubt. John Ruddy and Fraser Forster have come a long way in these last few years and are doing really well themselves and putting pressure on him. Ben Foster, when he gets fit again, will put pressure on Joe as well."

First of all, though, Hart must try to reclaim his club position.