Paul Merson has lambasted Chelsea's decision to allow experienced winger Willian to leave the club and join rivals Arsenal on a free transfer this summer.
The Brazil international's deal expired after an unsavoury contract stand-off brought an end to his seven-year Stamford Bridge spell, and his debut for Arsenal was marked by a hat-trick of assists against Fulham last weekend.
Merson says Chelsea have taken an unnecessary risk by not stopping Willian from walking away - and also insists Frank Lampard is now under pressure to deliver after a remarkable spending spree.
Chelsea were keen to keep Willian and thrash out an extension, but the 32-year-old had demanded a three-year deal. With the club only willing to offer him two years, Arsenal were able to capitalise and steal in.
'I cannot believe Chelsea let Willian go. I know they have gone out and got special players, but there is nothing to say they are going to hit the ground running,' Merson told Sky Sports.
'In Willian, you have got someone there who is ready-made. I like who they have signed, but they cost a lot of money, and their wages are probably the same as Willian.'
Willian won two Premier League trophies, an FA Cup, a Carabao Cup and the Europa League in west London before making the controversial move across the capital.
He starred on his top flight debut for his new club at Craven Cottage, while Timo Werner and Kai Havertz - two of Chelsea's big money signings - also made their bows in the scrappy win over Brighton.
Having sensationally splashed the cash to overhaul his ranks, Merson says that Chelsea's patience with Lampard may rapidly wear thin if he is unable to secure silverware soon.
He added: 'Frank Lampard has to win now. He has not got four years. That's management, I'm not being horrible.
'Even if Frank wins the league this year, it does not mean he is going to be there in four years. We know that and how it changes.
'Who is to say this is not going to take time for Chelsea? And I don't think they've got time at the moment.'