There were a handful of non-calls in the game and the Leafs didn't get their first power play of the game until past the midway mark of the 2nd period, well after the Blues had already had 3 power plays of their own. However, this missed high stick on Zach Aston-Reese was enough to make the Leafs, their coaching staff and the entirety of Leafs Nation's blood boil.
The reason why this was such a horrendous missed call by the officials is because the game was tied 4-4 in the final couple of minutes of the third period and, since Aston-Reese was left bloodied on the play, it should have been a double-minor, which would have resulted in the Leafs finishing regulation time on the power play and opened up OT with the man advantage, if necessary.
In the end, the Leafs picked up the win in overtime, but the officials still have some egg on their face after this one.