Hopefully you're right and it's not a terrible one. Based on next to no knowledge I'd have thought a break would have been better than ligament damage.
Re the tackle, I'm not sure I agree that those tackles aren't usually reds. Any time a player is jumping into a challenge it's a red or at least should be. As soon as a player leaves the ground they have zero control of their bodies, with 70, 80 or 90kg flying through the air. The moment that sort of force makes a clean connection with another player the chance of injury is huge and that's exactly what happened yesterday.
The ref didn't even blow for a foul, Baz. They are common tackles. You probably have seen that video of Maldini back in the 90s showing everyone 'how to win the ball back', its a similar situation.