Former Chelsea midfielder Frank Lampard says the club need to spend more on new signings if they are to compete with Manchester City and Manchester United at the top of the Premier League.
After losing Diego Costa and Nemanja Matic from their title-winning team in the summer, Chelsea invested around £190 million on five new additions -- Alvaro Morata, Antonio Rudiger, Tiemoue Bakayoko, Davide Zappacosta and Danny Drinkwater.
But Lampard says it will take an even bigger outlay to keep up the pace alongside City and United, with both clubs leading the Blues in the table.
"City and United have blown everyone else out of the water in terms of their spending in the last two years," Lampard told The Sun after he was named as the recipient of the Legends Of Football award in aid of the Nordoff Robbins charity.
"Chelsea have the power to match them but it's something they haven't particularly done in recent years. Don't get me wrong, they've spent good money. It's not as if they've suddenly stopped buying players. But other clubs are spending more and they have to be careful not to get left behind."
Chelsea's recruitment policy has reportedly left Antonio Conte feeling frustrated, with speculation that he could leave for a new challenge in the summer. And Lampard, who made more than 600 appearances during a 13-year spell at Stamford Bridge, sympathises with the Italian's situation.
"The manager isn't happy and he obviously feels his squad is a bit thin to battle on so many different fronts," he continued.
"And I think he's been proved correct to a degree because when you win the title and then lose big players like Costa and Matic, you have to recruit to move forward because everyone else is doing that.
"Antonio Conte certainly seems frustrated. He doesn't mince his words and he's been pretty honest about how he feels. I don't know where things are headed long-term but I think the club and manager will need to sit down in the summer to sort things out."
With the reigning champions 15 points behind Premier League leaders City, Lampard believes Roman Abramovich will continue to spend heavily to challenge for honours.
"Mr. Abramovich is not the sort of person to accept just finishing in the top four. That's why the club have been so successful over the last 15 years," he added.
"Chelsea spent something like £190m last summer but the landscape is constantly changing and you have to spend even more these days if you're going to get the top players.
"But I do believe the club will react to the challenge of the Manchester clubs and continue to fight for the major titles."