Chelsea goalkeeper Petr Cech insists Manchester United will feel the strain of their bid to win an unprecedented quintuple.
Chelsea narrowed the gap on United at the top of the Premier League to just four points with a hard-fought 1-0 win over Portsmouth at Fratton Park on Tuesday night.
Didier Drogba’s 79th-minute strike ensured a fourth straight win for interim boss Guus Hiddink however, Cech knows only too well how United’s quest for glory on all fronts can backfire.
Chelsea were on course for the quadruple in 2006-7 until early May but then had to settle for just the Carling and FA Cups.
Sir Alex Ferguson’s side are confident they will add the title, Champions League and FA Cup to the Carling and Club World Cup they have already won this season.
But 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.
"It is always tough. You need to have everything going for you, the momentum and luck to achieve it. It’s hard."
Meanwhile, Chelsea winger Salomon Kalou is happy to remain at Chelsea despite saying he would love to play under Arsene Wenger at Arsenal.
Kalou was approached by Wenger last summer and claimed it would be a ’dream’ to play for the Gunners. But the Ivorian has now clarified his situation
"I am very happy at Chelsea," he said. "For the moment, I’m playing well and I don’t see why I would be leaving.
"There are two years left on my contract and I’m happy at Stamford Bridge. Everyone supports me — the fans, my team-mates and the staff. So I don’t see why people have been worried by these rumours."
Portsmouth defender Sylvain Distin insists his side can escape trouble at the foot of the table if they continue to perform as well as they did against Chelsea.
But Distin is under no illusions about the task facing Pompey, who sit just two points off the relegation places and face fellow strugglers Middlesbrough in their next game.
Distin believes the south coast side have to win every game between now and the end of the season if they are to ensure top-flight football at Fratton Park next season.
"It was a good performance and we almost kept a clean sheet and against a team like Chelsea it was very good," said Distin.
"We are not going to lose every game if we carry on like we did against them. We will get the reward.
"I thought we had a good shape and organisation and are difficult to beat."