The action itself supposedly occurred during the third period's last minute goal mouth scramble in which Jason Spezza scored. Below is the broadcast footage from NBC Sports:
If you pay attention near the 16 second mark of the video, as the camera pans in you'll notice Girardi's left leg being forcefully pushed back by what I can only assume is Michalek's skate.
Although there's nothing conclusive from the broadcast feed of the kick itself, Bruce Garrioch has asserted that Shanahan has acquired the CBC footage of the play. If Giradri's claim is verified, Michalek could face a fine or suspension before Game 7 of the series on Thursday in New York.
It's worth noting that while the actual broadcast feed of the incident may not be evident, Shanahan will have access to footage from isolated cameras fixed on the play. In other words, in the broadcast feed, cameras cut away at different to points to capture different angles of the goal. Despite these change in angles, the other cameras never stop capturing footage. So if this alleged kick actually did take place, you can be sure that it will be on one of the 20-25 cameras had in the building last night.
As Garrioch noted in his article on the matter:
Michalek doesn't have any past history of bad behaviour with the league, but a source said Girardi was complaining after the game his pant leg was cut because of the incident. If Shanahan considers the incident serious enough for a possible suspension, a hearing would have to be held before puck drop Thursday night at MSG.If true, there's no defending Michalek. I suppose if there is any silver lining, it takes the attention away from his lazy and undisciplined second period penalty that was taken 200' away from the Senators net and helped contribute to the Rangers' first goal.
Per Chris Botta of the New York Times: