The hit occurred about 2 and a half minutes into the contest as the Avs were breaking the puck out of the defensive zone. Hall had lined up MacKinnon for a big open ice hit, but as MacKinnon shifted to try and avoid the check, his own stick got caught between his body and Hall's and ended up cracking himself across the face. You can see the play below.
The Avs took exception to the hit, with captain Gabriel Landeskog going after Hall, who refused to drop the gloves and answer the bell. The play was initially labelled a 5-minute major penalty, but was reduced to just a minor after a review of the play revealed that it was Mack's own stick that cause the damage. The picture below shows a bloodied MacKinnon on his way off the ice.
