Manuel Pellegrini has been sacked by West Ham following their 2-1 loss to Leicester on Saturday, but what went wrong for him?
The Hammers finished 10th in Pellegrini's first season in charge, but the latest defeat at the London Stadium has left them hovering dangerously above the relegation zone following a run of just two wins from their last 14 matches in all competitions.
The dip in form started when Pellegrini elected to field an under-strength team in the Carabao Cup third-round clash with Oxford United. The Sky Bet League One side duly thrashed them 4-0 at the Kassam Stadium - and things immediately started to unravel.
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Roberto unable to fill Fabianski void
West Ham allowed Adrian to depart to Liverpool in the summer, but it is a decision which will haunt Pellegrini after Roberto's struggles in the absence of first-choice goalkeeper Lukasz Fabianski, who suffered a serious hip injury in the 2-2 draw at Bournemouth in September.
Fabianski made more saves (149) than any other goalkeeper in the Premier League last season, while only Liverpool's Alisson (77) had a higher save percentage than the 34-year-old (72.5) of those goalkeepers who were ever-present.
West Ham lost just one of their opening six league games with the former Arsenal stopper between the posts, but they failed to win any of the seven games that Roberto started, and conceded 16 goals in the process.
The dramatic 2-1 defeat to Crystal Palace in early October was the 33-year-old Spaniard's first league start since April 2018 - and he looked rusty and out of his depth.
Roberto was at fault in their defeats by Everton and Newcastle, scored a calamitous own goal in the 3-0 loss to Burnley at Turf Moor - where he was also to blame for the hosts' second goal - and made more costly blunders against Spurs on Saturday.
It proved costly for Pellegrini, who eventually turned to his only other senior option, the 33-year-old David Martin, a free transfer from Millwall. Martin helped West Ham keep a clean sheet on his Premier League debut in the 1-0 win over Chelsea last month, but he was unable to prevent the poor results that followed it.
Poor recruitment proves costly
Sebastien Haller started strongly in the Premier League, scoring three goals in two games following the opening day 5-0 loss to Manchester City, but there is a growing feeling that defences have figured him out.
Haller was very effective last season with Eintracht Frankfurt playing as the focal point of a three-pronged attack, flanked by Luka Jovic and Ante Rebic, but he has looked isolated at times in a claret and blue shirt.
The Frenchman scored 20 goals last season, but a lack of pace has underpinned his struggles to replicate that return in east London. He has only scored two goals in his last 16 appearances in all competitions, and was substituted after 55 minutes during the defeat to Leicester.
In the summer, Pellegrini insisted on his old friend Mario Husillos being brought in as the club's new director of football - and it was his connection with Malaga that saw Roberto and Pablo Fornals arrive in east London.
Javier Hernandez was allowed to join Sevilla on the belief that Albian Ajeti could fill the void, but the Swiss forward has fallen short of the necessary quality so far - leaving little depth up front beyond Haller.
Given the imbalances in the squad and the question marks over the summer dealings, it's little wonder that Husillos is expected to follow Pellegrini through the exit door.
Hammers hamstrung by questionable selections
Fabianski is not the only important player who has been sidelined by injury this season. Michail Antonio's pace and physicality made him a big miss during his time on out between August and November.
But Pellegrini did not help matters with his team selections either.
Angelo Ogbonna was dropped after the 2-0 loss to Everton in October, but his replacement Fabian Balbuena did not inspire confidence.
Ryan Fredericks was also taken out of the side following that defeat at Goodison Park, but the fleet-footed full-back seemed the ideal option to counteract the pace of Allan Saint-Maximin when Newcastle came to the London Stadium a couple of weeks later.
Instead, Pellegrini left supporters bemused by selecting Pablo Zabaleta, and Steve Bruce's side wreaked havoc during a 3-2 defeat that flattered the home side.
There was more chopping and changing in the weeks that followed and the team looked unsettled as a result.
Speaking after Saturday's defeat to Leicester, former West Ham striker Tony Cottee told Sky Sports News: "Looking at the faces of the West Ham fans - they are so fed up with what's going on. They are on a really poor run of form. It's been coming for the last three, four weeks.
"Some of the decisions the manager makes baffle me. Haller was playing on his own. You can't play one up front at home; have a go. When they went behind they didn't look like getting back in it. When the manager made the substitution, he took off one forward in Haller for another in Antonio instead of going two up front."
Key players fail to find form
After West Ham lost their opening four league games last season, Pellegrini moved away from his preferred 4-2-3-1 formation and deployed a 4-3-3 system that allowed Declan Rice to flourish alongside Mark Noble and Pedro Obiang in midfield.
But Obiang has since been allowed to join Sassuolo, while Felipe Anderson - another who benefited from the change in formation - has now scored just one Premier League goal in his last 30 matches.
Rice's performances have dipped since he was criticised for his role in England's 2-1 defeat to Czech Republic in October, and the 20-year-old midfielder may only now be learning to manage the heightened expectations on his shoulders.
But he did at least give an honest appraisal following West Ham's defeat to Burnley before the international break in November, saying: "We were bullied all over the pitch - Burnley were winning everything. It's not good enough.
"It's been like this since the Crystal Palace game. We were nowhere near good enough. We haven't kicked on and we have been poor.
"There is a real buzz around the place during the week but when it gets to the game and we go 1-0 down our heads drop. We need to do the basics - the simple five-yard passing, the tackling."
Unfortunately for Pellegrini, that improvement never came.
Leicester defeat the final straw
Away victories at Chelsea and Southampton gave Pellegrini a little longer than many expected, but it felt inevitable that West Ham would sack Pellegrini after they were beaten by a second-string Leicester side on Saturday.
It was the Hammers' fourth straight home loss, leaving them just one point above the relegation zone. It was the final straw for the club and its restless supporters, who jeered Pellegrini's decision to substitute record signing Haller, rather than give him some support in attack.
A West Ham statement read: "Joint-Chairmen David Sullivan and David Gold, along with the board and everyone at West Ham United, would like to place on record their thanks to Manuel for his service over the past 18 months."
Sullivan said: "It is with great disappointment that we've had to make this decision. Manuel is a gentleman and it has been a real pleasure to work with someone of his calibre.
"However, it has become clear that a change is required to get the club back on track in line with our ambitions this season. We felt it was necessary to act now in order to give the new manager as much time as possible to try and achieve that goal."
Cottee, speaking to Sky Sports News, added: "I'm not surprised. West Ham were really poor. It's been coming for the last three, four weeks.
"I think the board have looked at it and thought, with a massive game coming up against Bournemouth, we've got to make a decision.
"I never thought it was the right appointment. The transfer policy has been dreadful."
Who next for West Ham?
West Ham have confirmed the re-appointment of David Moyes as manager on an 18-month deal and he will get straight to work against Bournemouth on New Year's Day.
"It's fabulous to be back," said Moyes. "It feels great to be home. I've missed being here because I really enjoyed it. I enjoyed being around the stadium and I loved being in this part of the world and I missed the club, so I can't wait to get started.
"I'm feeling very proud that I'm back here at West Ham. But I think more importantly I'll be looking to see what I can do and what I can make improvements to, how we can get some wins with the players and how we can get some quick wins on the field as well.
"I do believe that the squad of players I've got here is a better squad of players than when I took over before, so I am looking forward to working with them.
"I think there's got to be a short-term goal for us just now to get the wins to get us away from the wrong end of the league and what we're going to do over the next six months, then what we're going to do over the next period as well. The start is really focusing on the immediate games."
The former Everton and Manchester United boss took the reins midway through 2017/18 with West Ham in relegation trouble and led them to 13th, but departed the club soon after in favour of Pellegrini, a former Premier League title winner with Manchester City.
Moyes hinted he wanted to stay beyond his six-month contract, but despite achieving what he had been hired to do, he never appeared likely to be long-term manager.
With the relegation zone looming once again at the London Stadium, the powers that be will hope Moyes can produce a repeat performance.