Frank Lampard is considered to have “lost trust” in Kepa Arrizabalaga, with the hunt on for a new number one at Stamford Bridge
The Blues are expected to explore the option of bringing in a new goalkeeper this summer.
They already have the most expensive shot-stopper in world football on their books, but £71 million ($93m) man Kepa has struggled to convince across his two seasons in English football.
That has led to him falling out of favour and Lampard casting an eye over potential alternatives.
Chelsea have been linked with a number of keepers in the current window, from Andre Onana to Dean Henderson via Nick Pope and Marc-Andre ter Stegen.
Sinclair feels Oblak should be made the top target at Stamford Bridge, with a man widely regarded as the finest keeper on the planet considered to be capable of sparking a title challenge at Stamford Bridge.
“It’s not a secret that Frank lost this trust in Kepa,” former Blues defender Sinclair told Gentingbet. “In previous games he’s made some vital mistakes.
“However, you have to remember that he’s a really young goalkeeper, the £71m price tag shadows the fact that he’s a young goalkeeper, fairly inexperienced in playing senior football and the standards are set very high for him.
“At the same time, if you get the opportunity to bring in Jan Oblak then I think if you want to compete with Liverpool and Manchester City, Chelsea need a goalkeeper of the same standard and certainly Jan Oblak would produce that.”
While looking to address issues between the sticks, Chelsea are also in the market for reinforcements across their back four.
Leicester left-back Ben Chilwell figures prominently on Lampard’s wish list, but Sinclair says the Blues should avoid paying “over the odds” for a player who is far from being the only option available to them.
He added: “Ben Chilwell is still a tough nut to crack.
“When you hear the way that Brendan Rodgers talks about Ben Chilwell, so strongly and how much [he is] a part of Leicester City going forward, I guess it would be a difficult one and he’s always going to be a very, very overpriced signing.
“For me, there’s a lot of world-class full-backs out there and Frank has to get the right one for Chelsea Football Club.
“Obviously Ben Chilwell is a top player and England international, but I don’t think Chelsea should pay over the odds for him.”