Fabregas said: "I know they will always regret not going to the World Cup but for us the benefit has been amazing. They had seven weeks' holiday and you can see the results of that rest.
"We are so delighted they are in such great form.
"We went to the finals and have struggled with injuries since then.
"So the World Cup has made a very big difference. Not just to us and not just to the other top clubs - but to the whole Premier League.
"It's all a little bit weird."