Former Tottenham and Barcelona boss Terry Venables says this month's transfer market will make or break club's fortunes this season.
In his column for The Sun, Venables wrote: "The transfer window opened this morning.
"And, with the battle at the top the most open for years, the decisions and deals made by the contenders over the next 31 days could have an impact on the destination of the trophy like never before.
"The winter window is usually the salvation of the clubs at the bottom of the table.
"A time when the West Hams, Wolverhamptons, Wigans and Birminghams of this world can bring in signings to refresh their ailing squads and boost their bids for survival.
"Their rivals at the opposite end of the table have, by and large, turned up their noses at the thought of doing expensive business midway through the season. But with the chase for the title now a five-horse race instead of a two-horse one, that looks set to change this term and this could be the most important January window. Ever.
"Just five points separate leaders Manchester United and fifth-placed Tottenham - with Manchester City, Arsenal and Chelsea in between. Those are the five clubs vying for the title and it is maybe even too close to call.
"All five clubs could do with strengthening their squads this month - although all five will not, of course."