West Ham's season has finally got underway with the club slowly settling into life at their new ground, the London Stadium.

The move has brought mixed fortunes for the Hammers but Slaven Bilic's boys have lost just once in six games and their ambitions remain as high as ever.

To achieve the ambitions the owners have laid out for them, however, they must improve the depth within the squad.

The over-reliance on Dimitri Payet is still a paramount issue with West Ham struggling to capture any form without their talisman hitting top gear.

If the club are to break into the European places finally, then Bilic must invest this winter to secure the club's place in the continental competitions.

Some positions require the necessary attention to improve what's already at the Irons' disposal.

And with all this taken into consideration, here are four heavyweight purchases West Ham should consider making in the January transfer window.

ST: Alexandre Lacazette

West Ham were heavily linked with Alexandre Lacazette during the summer. A bid was rejected by the Ligue 1 outfit Lyon, but Bilic must consider a higher offer this winter transfer window with both clubs struggling for form.

Lacazette's dynamism and flexibility to play anywhere across the front three would give Bilic considerable options. The Lyon striker is a proven goalscorer which is something the Hammers are desperately missing.

RW: Alex Oxlade-Chamberlain

The Arsenal winger would be the ideal addition to the London Stadium, providing the necessary pace and speed on the wing – perfect for a pitch the size of the Irons' new home.

Chamberlain desperately needs to move away from the Emirates Stadium with his career stagnating. A move could cost West Ham in excess off £25million, but it would be brilliant business considering he's still only 23.

Wenger could be open to selling Chamberlain if the former Saints winger opted to leave the Emirates Stadium.

CM: Yaya Toure

Take away his mouthy agent, and you have one hell of a player. Even at the age of 33, Yaya Toure would make a brilliant signing for West Ham.

His Premier League experience added with his still evidently brilliant ability would ensure the Hammers' squad is capable of mounting a serious challenge for the top seven.

Toure's City career looks set to end following a dispute with Pep Guardiola, and Bilic could re-inject the necessary love to retrieve the best out of the Ivorian.

CB: Kevin Wimmer

Austrian international Wimmer is likely to depart Tottenham in the coming months as his lack of first-team football is becoming something of a worry.

The form of Toby Alderweireld and Jan Vertonghen make it nearly impossible for Wimmer to impose himself on the Tottenham team.

At West Ham, the 23-year-old could be the ideal long-term replacement for James Collins, who is struggling to maintain the necessary form demanded by Bilic.

A Wimmer and Reid partnership in central defence may provide the Irons with the much needed security that is craved at the back.