The 27-year-old Spaniard joined the Blues last summer but rarely played in the Premier League, making just 10 appearances.
Thomas Tuchel signed Niguez to strengthen his squad ahead of a potential title challenge last year. However, there was no inclination to compete with Liverpool and Manchester City.
According to Marca, Niguez has already returned to his home club Atletico Madrid after the end of the season.
His departure leaves Chelsea in midfield, with N’Golo Kante missing much of last season through injury, while Billy Gilmour’s introduction to the first-team could be put on hold after a disappointing spell at Norwich City.
New owner Todd Boehly is reported to be backing Tuchel with a sizeable war chest in the transfer market, but the delay in his takeover seems to have upset Chelsea’s summer plans.
Declan Rice is believed to be wanted by the Blues but West Ham’s valuation of over £100m means a deal is unlikely to materialize.
Meanwhile, another target – France and Monaco midfielder Aurelien Tchouameni – is said to be close to joining Real Madrid.
In addition to midfield, reinforcements are needed in defense with Andreas Christensen and Antonio Rudiger both leaving Stamford Bridge.
Due to the goal fights in the past season, Tuchel also wants new strikers this summer.
Towards the end of last season, the German said: “If we stick with the group, we will try to solve it with these players. Is it necessary to bring more attacking players to the box to create more distraction to create more space for each other?
“We’re going to ask that question. Can we make the structure better? Can we push the players more? Did we film too much? Just take a look. There are many opportunities.
“The numbers we’re producing from our attacking players don’t allow us to overperform and we need overperforming if we want to be closer to the top two teams.
“I’m not pointing fingers, I’m not blaming anyone, but we need an overperformance from everyone. It’s not an overachievement if we only have single-digit goals and assists.”
MORE: Chelsea ‘very interested’ in beating Arsenal against Manchester City star Gabriel Jesus
MORE : Chelsea favorites sign wanton Barcelona striker Ousmane Dembele on a free transfer
For more stories like this, visit our sports page.
Follow Metro Sport for the latest news
Facebook, Twitter and Instagram.
https://metro.co.uk/2022/06/07/chelsea-transfer-flop-saul-niguez-leaves-stamford-bridge-16787412/ Chelsea transfer flop Saul Niguez leaves Stamford Bridge | Soccer