Exclusive - West Ham are looking at a number of central defenders from around Europe, including Shakhtar Donetsk's Mykola Matviyenko and Valencia's Mouctar Diakhaby.
The Hammers are gearing up for a maiden appearance in the Europa League group stages, having secured a superb sixth-placed Premier League finish during 2020/21.
But despite the need to bolster David Moyes' squad with new additions, West Ham have only loaned in goalkeeper Alphonse Areola from PSG to date - the club's other new arrivals are young players who are unlikely to play a prominent first team role this season.
There is money to spend at the London Stadium this summer and 90min understands that alongside interest in signing an attacking midfielder - Jesse Lingard, Matheus Pereira and Ross Barkley just three of the players West Ham have looked at - there's a real desire to strengthen Moyes' backline.
One name on the Hammers' radar is Matviyenko, who has been of interest to the club for around a year. 90min revealed in August last year that he was a target for not only West Ham, but also Everton, Wolves and Leeds. He has experience of playing in the Champions League and was watched by Arsenal prior to their signing of Gabriel Magalhaes from Lille.
Another player that West Ham are monitoring is Valencia's Diakhaby, who has three years of La Liga experience under his belt. The 24-year-old is excellent in the air and also has experience of playing in both the Champions League and Europa League.
There's also reported interest in Chelsea centre-back Kurt Zouma, with Sky Sports suggesting that contact has been made over a potential £20m move. The 26-year-old is likely to be leaving Stamford Bridge this summer to pursue regular first team opportunities - something he's unlikely to be afforded in west London should Jules Kounde arrive from Sevilla.
Indeed, Zouma could even be on his way to Spain as part of the deal, although it's believed that he's settled in London and would prefer to stay in the Premier League if possible. Chelsea's valuation is thought to be higher than £20m, which could prove problematic for the Hammers given their desire to invest elsewhere.
West Ham are also interested in striking a deal with Slavia Prague for Czech Republic winger Lukas Masopust. He's a former teammate of both Tomas Soucek and Vladimir Coufal, and could be available this summer for as little as £6m.
There is competition for his signature, however, as Leicester, Watford, Brighton, Newcastle, Wolves and Crystal Palace have also been offered the chance to sign him.