Barcelona's technical secretary Robert Fernandez and his assistant Urbano Ortega reportedly travelled to London earlier this week to watch Monday's (6 March) derby between Chelsea and West Ha, and the Champions League encounter between Arsenal and Bayern Munich on Tuesday night. Marca claims the reason behind their mission was to spy Cesar Azpilicueta, Marcos Alonso, Nemanja Matic and Hector Bellerin.
The La Liga giants were already heavily linked with Azpilicueta and Bellerin during the summer transfer window but eventually decided against signing any right-backs, opting instead to give a chance to versatile Sergi Roberto and Aleix Vidal to convince Luis Enrique they could cope with the departure of Dani Alves.
In November Bellerin appeared to have ended Barcelona's hopes of signing him after signing a new long-term deal at Arsenal, reportedly worth around £100,000 per week.
Azpilicueta, meanwhile, followed a similar pattern a month later committing his long-term future to Chelsea following an impressive campaign playing as a centre-back in Antonio Conte's 3-4-3 formation.
However, speculations have resurfaced after reports in Spain recently indicated Barcelona have earmarked the signing of a right-back as its top priority for the coming transfer window.
Marca's reports that Barcelona's technical secretary and his assistant's clandestine visit to London earlier this week to spy on both Azpilicueta and his Arsenal compatriot Bellerin might further lend credence to the claims.
The Spanish publication claimed the Catalans also ran the rule over Matic and Marcos Alonso after the latter recently revealed to IBTimes UK that he had already been approached by Barcelona before making his summer move to Chelsea.
Marca, however, observes that luring any of the players away from Chelsea or Arsenal will be difficult due to the Premier League's hefty wage packets.
Furthermore, Azpilicueta will be even more difficult to prise away from Stamford Bridge after Conte recently said the Spaniard "is one of the best in the world in this role", and a key member of his 3-4-3 formation.