The World Cup is not only football's biggest tournament, but it also serves as a shop window for players to impress onlooking clubs.
Jose Mourinho's first season back at Chelsea ended in disappointment as the Blues failed to land a trophy, but fans can be confident that they will mount a title challenge next season having come so close this time around. Mourinho will now be planning a summer of spending in order to get Chelsea over the finish line, and some World Cup stars may be of interest.
With central midfielders and strikers needed at Stamford Bridge, you can be sure that Mourinho will be bringing some new faces in to fill those holes, whilst depth could also be added to the defence. With that in mind, here are five stars playing in Group E at this summer's World Cup that could fit the bill.
Raphael Varane, France
The Real Madrid star emerged under Mourinho in the Spanish capital, and is set to partner Laurent Koscielny in the heart of the French back four this summer. An athletically gifted defender with great ability on the ball as well, Varane is still only 21 and is already one of the top defenders in the world. With David Luiz on the way to Paris Saint-Germain and John Terry's career drawing to a close, Mourinho could look to reunite with Varane this summer.
Eliaquim Mangala, France
If Mourinho can't land Varane, then he may turn his attention to another French centre back - Porto's Mangala. The former Standard Liege star has really emerged as one of the top young defenders in Europe this season, and the Portuguese club have slapped a £35m price tag on his head. The Blues have to add a centre back this summer, and with a credited interest in Mangala, he could be the one.
Paul Pogba, France
Finding a long-term partner for Nemanja Matic in the centre of midfield is a definite need for Chelsea this summer, and whilst speculation suggests they will look to bring Atletico Madrid's Tiago back to Stamford Bridge, splashing out for a young star like Pogba could also be an option. The former Manchester United man has proven his worth in Italy with Juventus, but could cost up to £50m after a superb season.
Ricardo Rodriguez, Switzerland
The departure of long-serving left back Ashley Cole means Chelsea have a huge hole to fill in their defence. It seems they have lost out to Manchester United in the race to sign Southampton's Luke Shaw, and Mourinho will turn his attention to other targets such as Wolfsburg's Rodriguez. The 21-year-old has enjoyed a superb season in the Bundesliga and has been linked with Chelsea for almost a year now - a strong showing at the World Cup could be the confirmation the Blues need to make a move for him.
Fabian Schar, Switzerland
Whilst Varane and Mangala would cost big money to sign, an under-the-radar target could be Basel centre back Schar. The 22-year-old made himself known after impressive Champions League displays against Chelsea, and after seeing former Basel team mate Mohamed Salah clinch a move to Stamford Bridge in January, Swiss defender Schar could be a dark horse to join him this summer if he impresses on the world's biggest stage.