Playing Croquennis is less risky than using a public footpath and is probably one of the safest outdoor sports that can be played.
The principle risks are (1) trips over the hoops, a croquet mallet left on the ground, or a ball,or a line marker, (2) slips when the lawn is wet, (3) exacerbating any previous hand injury, (4) chemical contamination from chemical use on the lawn, (5) contamination from several users using the same mallet. (6) sprains from bending down to gather or place a ball, clear leaf mould etc. (7) sun burn or dehydration on hot days (8) personal medical conditions that could impact you whilst playing eg allergy to wasps (9) Contamination from dog or animal mess or dog or animal contaminated hoops.
All of these are extremely low level risks.
There are also risks in setting up and taking down the hoops and you should adhere to any manufacturers instructions.
The risks can be mitigated by following the rules below:-
Never walk through the hoops, always around them
Always check the whereabouts of the ball and the markers before moving around your half of the court
Never leave a mallet horizontally on the ground
Never yank a hoop out of the ground. if it resists a simple lift. Get help, or leave it there until the ground softens
Wash hands after playing
Do not play when the lawn is wet or frosty (walking on frost can damage the lawn too!)
Stop playing if at all uncomfortable in the hands, legs or back.
If appropriate, tell the other player what to do in the event of a medical emergency that could happen to you.
Take a mobile phone with you to call for help in the event of an emergency.
Take a bottle of water and use sunblocker as appropriate.
Reporting any dog or animal intrusion and politely asking owners of invading animals to keep them off the lawn.