Chelsea representatives are becoming increasingly familiar with Valencia's hierarchy this summer as they try to bolster Antonio Conte's squad ahead of the new season.
The Blues have been trying to negotiate a deal for Portuguese international Andre Gomes but have so far struggled to make much progress.
And following news that one of their other top transfer targets is set to stay at his current club, Chelsea have turned their attention to another one of Valencia's big names.
Conte had been hopeful of enticing Leonardo Bonucci to join him at Stamford Bridge after impressing at Euro 2016 but with the player satisfied at Juventus, the new Chelsea boss is now considering a move for Shkodran Mustafi, according to The Mirror.
Traditionally a key strength, the Blues' defence looked frail throughout the course of last season. An ageing John Terry and Gary Cahill were overly exposed, causing Guus Hiddink's side to ship 53 goals in the Premier League, 19 more than Jose Mourinho's title-winning team did just 12 months earlier.
Chelsea made a U-turn on the future of Terry by offering him a new deal at the beginning of the summer but Conte has recognised he will still need to add at least one more defender before their first league game against West Ham on August 15.
Mustafi would therefore be a welcome addition at Stamford Bridge. The 24-year-old has been at the Mestalla since 2014 and was also part of Joachim Low's German squad to win the World Cup two years ago.
He was being tracked by Barcelona before they opted for Frenchman Samuel Umtiti, which should make any pursuit for Mustafi much easier for Chelsea.
Gary Neville's ex-employers Valencia had a torrid season last time out and know it is unlikely they will be able to keep hold of both Mustafi and Gomes by the time the transfer window closes in September.
The Mirror suggest an offer over £25 million would be required to tempt the centre-back's current team to sell up.
Conte's Chelsea reign didn't get off to the best of starts yesterday and his new side suffered a 2-0 defeat to Rapid Vienna in the first game of pre-season.
Despite confirming a deal for N'Golo Kante, the defeat further highlighted the Italian's need to prioritise defensive reinforcements in the coming months.