Manuel Pellegrini is under pressure at West Ham after a seven-match winless streak plunged them towards the relegation zone.

Here, the PA news agency looks at five things that have gone wrong for the Hammers boss.

Casualty curse

Not for the first time West Ham have been hit hard by injuries this season. Michail Antonio has been a big miss, out for three months with a hamstring injury, while Manuel Lanzini is out until the new year after suffering a fractured collarbone. Jack Wilshere has hardly been seen, but by far the biggest loss has been goalkeeper Lukasz Fabianski, who remains sidelined with a hip injury. Which brings us to...

Jeepers keepers

When West Ham reluctantly let back-up keeper Adrian leave in the summer, and replaced him with 33-year-old Spaniard Roberto, few could have predicted the horrendous impact. The injury to Fabianski, West Ham's player of the year last season, thrust Roberto into the spotlight and he immediately froze. Disastrous display after disastrous display has seen the Hammers fail to win any of the eight matches since he came into the team. The defenders have been drained of confidence and the opposition have been virtually gifted a goal head start, at least, in every game.

Blooper Mario

Roberto is far from the only summer signing to have disappointed, leaving the role of Mario Husillos, the club's director of football and one of Pellegrini's most trusted allies, under increased scrutiny. Striker Sebastien Haller has shown potential, but for £45million that is the least to be expected. Midfielder Pablo Fornals has so far only illustrated just how little £24m gets you these days and that signing looks even more frivolous given Pellegrini already had the likes of Lanzini, Felipe Anderson, Robert Snodgrass, Andriy Yarmolenko and, notionally at least, Wilshere, to fill the same position.

System addict

Pellegrini's unshakable belief in his attacking philosophy, when it works, is one of his most endearing qualities. However, the 4-1-4-1 system has its flaws and while it is all very well filling your side with flair at Real Madrid and Manchester City, it is not working at West Ham. It is no surprise that the more muck-and-nettles players such as Declan Rice, Snodgrass and captain Mark Noble are the ones avoiding criticism from the stands. West Ham have too many Cavaliers and not enough Roundheads, and cup exits to AFC Wimbledon and Oxford suggest Pellegrini cannot motivate them.

Missing in action

The crux of the matter is that, ultimately, too many big players are not performing. Anderson, previously the club's record signing, looks a shadow of the player of last season. Yarmolenko comes and goes, Lanzini has not been able to recreate his form of two years ago and, as a result, Haller looks isolated and increasingly frustrated. There are strange selections, too. Left-back Aaron Cresswell's levels have dipped alarmingly, yet Arthur Masuaku cannot even make the bench. Nevertheless, the worry for Pellegrini is that the players have stopped playing for him, and when that rot sets in there is usually only one outcome.