West Ham United boss Sam Allardyce says they cannot afford a quiet summer market.
But the Upton Park boss said: "The financial restrictions kick in this year so we will have to be careful in respect of how we spend our money.
"We'll have to see how it pans out but it can make things a bit more difficult, though hopefully as a team we can still get better.
''What people don't always understand is that small improvements are so difficult to achieve.
"Everybody expects a £12m player to improve a team by 15 or 20 per cent but often it's only one or two per cent.
''The size of the fees for players brings more pressure on the manager because they can be astronomical at times."