Rugby has helped Petr Cech to resume his career three months after surgery on his head.
Cech is fit again after suffering a fractured skull at Reading in October, but must wear a special headguard until specialists are satisfied there is no danger of further problems.
Cech's headguard has been specially designed by the New Zealand-based company, Canterbury, which specialises in rugby equipment, including scrumcaps.
Chelsea's medical department contacted Canterbury last week to commission a bespoke version of the rugby cap the Czech international has been wearing in training, with extra protection to cover the areas of his skull weakened by the collision.
The cap has been shipped in from New Zealand in time for the goalkeeper's possible comeback against Liverpool today.
The referee, Rob Styles, who will officiate against Liverpool, inspected the equipment on Thursday and the FA's head of senior referee development, Neale Barry, said: "As headguards are not part of a player's 'basic compulsory equipment' as set out in the laws of the game, it's essential that they are safe to wear.
"This headguard is soft in construction, with padded areas of dense foam all over to protect the head of the wearer. It covers the ears but there's a hole on each side so that his hearing is unaffected.
"The helmet could cause no risk to the safety of either the wearer, or any team-mate, or opponent. It has no areas on the helmet that could cause unnatural deviation of the ball if it were to either strike the helmet or if the wearer were to head the ball."
Jose Mourinho, also gave Cech the all-clear, saying: "I cannot tell you if he is playing, because the goalkeepers have to be the first ones to know my decision, but he is ready."