Depends on the degree.....1st, 2nd, or 3rd.
The ligament can be stressed upon landing directly on the joint. If the acromion process and end of the clavicle share the brunt equally, it tends to be a grade 1 unless the player lands from a high free-fall.
If the impact is more off center (which is usually the case because the acromion is more prominently positioned) the acromion is driven downward and the ligament stretches (within its span between the acromion and the clavicle). Grade 2.
In a more violent event (in terms of acromion being driven downward) a grade 3 sprain can occur. This is a complete rupture of the ligament (ligaments don't stretch very far before they fail) The clavicle pops upward and looks like a diving board.