I'm going to go out on a limb here... IMO Eichel's "laziness" will make him prone to these type of awkward falling injuries. By laziness, I mean poor posture on the ice. For guy with his size and strength, you'd think he'd be able to hold his ground but when he's not engaged, not ready for battle, just cruising out there... he puts himself into bad situations.
This latest incident... if you watch it closely... instead of falling forward, or just dropping down to his knees... he falls backwards. Watching it in slow motion, there's no reason for him to fall backwards unless his weight was on his heels. His weight should've been on his toes, ready to engage the Bruin defender. Instead he has his weight on his heels, in a relaxed stance. Same thing happened with the Girgensons incident. His weight was on his heels, he fell backward awkwardly. When you're engaged in a net front battle your weight should be on your toes, giving you leverage against the defender and protecting you from falling backward.
In both cases, IMO he's just too careless, not engaged, not ready for battle, leaning back on his skates like he's out for a public skate. Every second of every shift you need to be on your toes, ready to react and absorb contact. I don't think he's figured that out yet.