Petr Cech believes Manchester United will crack under the strain of trying to win the Quintuple and warned Chelsea will make them pay for any slips.

The Blues cut the gap to United at the top of the Premier League to just four points with a hard-fought 1-0 victory at Portsmouth, which was the club's fifth straight win in all competitions.

Cech said: “It's hard when you want to win every competition — we know because we have gone close before. You can have a bad day and sometimes it's not even that, it's just bad luck. Sometimes you hit the woodwork three times and then concede at the other end and you're out of a competition.”

Sir Alex Ferguson's side, who travel to Newcastle tonight, are confident they will add the title, Champions League and FA Cup to the Carling Cup and Club World Cup they have already won this season.

But Cech knows how tough it is to keep fighting on all fronts with Chelsea having been on course for the Quadruple in 2006-7 until early May, only to end up finishing the campaign with just the Carling and FA Cup.

He added: “It is always tough, you need to have everything going for you, the momentum and luck to achieve it. It's hard.”