The thing with ACL injuries, especially ones that require major surgery to fix, is that it can take a lot longer than the physical recovery time to fully heal. I've heard it mentioned by some physiotherapists that if you need 6 months to recover physically, you'll need up to another 6 months on top of it to recover psychologically.
In my personal life experience, over the years I've had ACL reconstructive surgery performed on both knees, and for me it definitely took quite a while to trust my knees wouldn't give out on me when doing such mundane tasks like walking down stairs or even standing up out of bed in the morning. Even though they were probably totally stable due to the successful surgeries, my brain would play tricks on me.
Hopefully Sekera won't have similar issues, because we need him on the ice and performing at the best of his abilities. And we need it yesterday.