The 2018 World Cup is well underway and there are a number of nations that have impressed and players that have already made a big impression for their country in their opening group game, and surely some of them will have caught the eye of West Ham United manager Manuel Pellegrini.

The Chilean boss will be determined to strengthen his newly-inherited squad this summer in order to ensure they significantly improve on their 13th-place finish in the 2017/18 campaign, and he has already completed deals for Fulham right-back Ryan Fredericks and Toulouse centre-back Issa Diop.

The former Manchester City chief, who has been urged to sign a £16.2m-rated midfielder following a stunning World Cup display, certainly won't be finished there, and he will want more quality additions to his side in order to ensure they he maintains his record of never finishing lower than seventh while during his managerial career in European football.

He will already have his targets in mind, but he may well have been convinced by the displays of some individuals in Russia, too.

Here are three World Cup stars that Pellegrini has surely added to his summer transfer wishlist…

With Jose Fonte and James Collins both leaving the club in recent months and continued worries over the fitness of Winston Reid, one of Pellegrini's priorities during this summer transfer window will be to strengthen in central defence, even after the addition of Diop.

One player that should have caught the Chilean manager's attention is 20-year-old Fiorentina starlet Nikola Milenkovic, who shone for Serbia in their 1-0 win against Costa Rica on Sunday.

The towering centre-half would bring some height and pace to the Irons backline, and he looks to have a really bright future ahead of him.

Following a largely disappointing 2017/18 campaign for West Ham central midfielders Mark Noble and Cheikhou Kouyate, Pellegrini may well want to add a new player in the middle of the park this summer.

The Sun on Sunday reported on June 18 that the east London club feel they are in a good position to sign Jack Wilshere, but perhaps they should turn their attentions to Huddersfield Town's Mooy instead.

The Australia international was hugely impressive on and off the ball in his nation's narrow 2-1 defeat to France on Saturday, and with the Premier League experience and quality he clearly has he could be an inspired addition for the Irons.

A serious injury for Manuel Lanzini while on pre-World Cup duty with Argentina means that the 25-year-old is likely to be on the sidelines until early 2019 at the very earliest, and it could mean that Pellegrini ups his search for a new attack-minded midfielder.

The Chilean may well have been impressed with Sao Paulo forward Cueva's display in their 1-0 defeat against Denmark on Saturday, despite the fact he blasted a penalty kick over the crossbar.

It was certainly a jot on the 26-year-old's copybook in what was a standout attacking display, where he impressed with his pace and skill and had two shots, as well as completing four key passes and two dribbles, as per WhoScored.com.

Do you agree, West Ham fans? Let us know below.