It was sad to see Clarke leave the field at the Adelaide test and even worse to see that he has to have surgery. So what is the reason for this - why does Clarke need surgery when most hamstring issues don't?
The introduction of high quality MRI scans over the last few years has allowed for much more information to be gathered on specific injuries. The common hamstring injury involves the muscolotendinous junction - where the tendon overlaps with the muscle. These are the 'typical', 3-4 week injuries.
Separate to this, the hamstring tendon that attaches to the pelvis can be torn or ruptured. This isn't good! These normally need surgery. This however is not what it appears Clarke has had happen as he grabbed the middle of his hamstring.
There is an isolated area of tendon within one of the hamstrings that can be torn. These are quite rare and only started being noticed a few years ago. Other high profile athletes to have these injuries include Nick Reiwoldt and Sam Mitchell. I've had a decathlete through with the same injury. These are tricky! They tend to take 12-16 weeks for full recovery whether treated with or without surgery. However with surgery the recurrance rate is thought to be lower. It appears that this is what Clarke has had happen last week.
So the upshot for Clarke is that we are unlikely to see him back at 100% until mid March or perhaps mid April. Let's hope he rehabs well!