Senior Chelsea players are becoming concerned over the lack of progress on transfers so far made.
The London Evening Standard says Chelsea are beset with uncertainty. The club are yet to act on the future of coach Antonio Conte, despite holding talks with possible replacements, while they have been without a technical director since Michael Emenalo left last November.
Some of their rivals have already started strengthening ahead of the next Premier League campaign, despite the inconvenience of the World Cup.
The Belgians, who have two years and one year left on their contract respectively, have urged Chelsea to show ambition during the close season.