#2 Eden Hazard
The Belgian wizard needs no introduction and he is undoubtedly one of the best players in the world. On his day it is impossible to stop him and he is a player capable of winning trophies single handily.
Chelsea have a simple formula to win trophies: keep Hazard in good form and he will deliver. Even this season as well when the whole team had issues all over the pitch Hazard performed really well and won Chelsea the FA Cup.
The former Lille winger is a target for Barca's arch rivals Real Madrid and if the Catalan giants manage to snap him up under the noses of the Los Blancos, it will be a big blow to them. If he arrives at the Camp Nou it will be a dribbling nightmare for defenders, as in Hazard and Messi, they will have two dribblers who are statistically the best in Europe.
Also, he and Griezmann are likely to cost the same price to Barca and Hazard represents more value for money compared to Griezmann. Hazard is more of a winner than the Frenchman and overall a better player as well. The Chelsea's talisman also has just two years left on his contract and the Blues might be tempted to sell him as well.
If he wants to challenge for major honors every season Barcelona might just be the perfect club for him. Also, Eden Hazard can also flourish in Barca's attacking style of football and enjoy more freedom, something he does not have at Stamford Bridge, due to Chelsea defensive tactics.