There could be no greater contrast between West Ham's summer transfer window and their start to the season in the Premier League.
Indeed, owners David Gold and David Sullivan made it clear the club were taking an ambitious approach in the transfer market to mark their historic move to the London Stadium.
13 players were brought in at a cost exceeding the £50million mark, but that investment hasn't translated into positive results.
The Hammers have lost four games in a row in the Premier League - as part of a record of six defeats in nine across all competitions - and now find themselves battling it out in the relegation zone, albeit after just five games.
It's not hard to see where the problems lay; whilst West Ham have scored seven times this season, the best return of any Premier League side in the bottom half, they've conceded 13 goals, giving them second-worst defensive record throughout the division.
And whilst plenty was spent on improving the Irons' quality in the middle-to-final third during the off-season, it now seems not enough attention was paid to a backline that conceded more than 1.3 goals per match last term.
With that in mind, we've taken a look at five defenders Slaven Bilic should have signed during the last transfer window...
ASHLEY WILLIAMS
Considering Ashley Williams is firmly established as one of the most consistent centre-backs in the Premier League and more than proved his quality on the international stage with Wales during the summer, it's rather incredible that Everton snapped him up for just £12million. That sum was more than affordable for the Hammers; the Toffees, meanwhile, have kept clean sheets in two of the defender's first four Premier League appearances.
VEDRAN CORLUKA
He's well acquainted with Slaven Bilic via the Croatia set-up, boasts prior Premier League experience with Tottenham Hotspur and Manchester City and can even play at right-back - which has been arguably the Hammers' biggest problem area so far this season. Indeed, Vedran Corluka would have been a very impressive addition to the Hammers' defence and some unsubstantiated reports even claimed his contract was winding down. But the Irons never made a move and the 30-year-old remains at Lokomotiv Moscow.
NICOLAS N'KOULOU
Nicolas N'Koulou is one of Ligue 1's better defenders, twice claiming a spot in the division's Team of the Year whilst amassing 68 caps for Cameroon, and was available on a free transfer this summer after five largely successful seasons at Marseille. The 26-year-old signed for Lyon instead and has gone on to claim three clean sheets in five league appearances.
MAMADOU SAKHO
Mamadou Sakho's attitude may come under question after being sent home from Liverpool's pre-season tour, but that's exactly why he was there for the taking this summer. The France international has firmly got to grips with the Premier League after three years at Anfield and even if he's not exactly a world-beater, his physicality could have been a real asset for the Hammers at the back. Furthermore, the 26-year-old can slot in at left-back if necessary and is certainly more sturdy defensively than summer signing Arthur Masuaku.
BEN DAVIES
Another Masuaku alternative the Hammers should have moved for; Ben Davies proved his quality with Wales at Euro 2016 but still finds himself behind Danny Rose in the pecking order at Tottenham Hotspur. At 23 years of age, the left-back could quickly flourish with the level of game-time West Ham can offer in the absence of injured No.3 Aaron Cresswell. Admittedly, whether Spurs would have done a deal with the Hammers - and at what cost - remains open to debate. But rather than boosting Slaven Bilic's defensive options, Davies is spending the season as second-fiddle to Rose.