Gianluca Vialli believes Chelsea's poor start to the season can be blamed on their struggles in the transfer window.

Champions Chelsea have taken just four points from their first four Premier League games – a far cry from the form that saw Jose Mourinho's side go unbeaten until December and romp to the title last term.

Mourinho's toils in the window were well documented, as the Portuguese failed to land his main defensive target, Everton's John Stones, and made only one marquee signing in the form of Pedro from Barcelona.

Former Chelsea manager and striker Vialli thinks the club are now feeling the consequences of their inability to freshen up their title-winning squad, but he also expects Mourinho to rectify the situation sooner rather than later.

Speaking to Omnisport at Soccerex, Vialli explained: "Firstly, it's always difficult to start again with the same level of motivation after you've won the championship – even if you're managed by someone like Jose Mourinho or Alex Ferguson. 

"Secondly, I think the transfer activities for Chelsea have been very quiet. 

"After winning something, you need a sparkle, you need someone new coming in with desire and willing to share the motivations with the rest of the players – it's good for the mood of the camp and it didn't happen with Chelsea until Pedro came in.

"Compare that to the previous year when they got [Thibaut] Courtois, [Cesc] Fabregas and Diego Costa – in every department they had a new face and that created a lot of momentum. 

"It's not happened this year so it's a struggle, but now with the international break and the sort of manager Mourinho is, I think he will be able to turn it around."

Expanding on Chelsea's below-par window, Vialli expressed some sympathy with Mourinho.

"I think they did amazing for the last two or three years, selling players at astronomical amounts of money and getting very good players for reasonable money," he added.

"They were trying to achieve that last summer – sometimes it works, sometimes it doesn't. 

"Sometimes you end up empty-handed or not being able to achieve what you wanted. At Chelsea, rightly, they prefer not to sign players for the sake of it. 

"Also, I'm a big fan of teams that don't change too much. It's not that Chelsea are not good enough, they are, it's just a matter of making sure they reconnect and they find that hunger again.

"It's not easy to strengthen when you already have a great side. There are not that many players out there who are better than yours. 

"I think defensively they wanted to do more – in the midfield, perhaps one player, but I think up front, [Radamel] Falcao can be a very good signing. He's capable of scoring lots of goals in the Premier League."