Not criticizing, but observing...
In the Blues game, I stayed out of the GDT because I watched on DVR delay later that evening.
On Tarasenko's 2nd goal, the Blues ran a set play off the faceoff in their zone. D-man banked a pass off the boards out of Power's (and Tarasenko's) reach, allowing Tarasenko to collect it off his own carom with position on Power to get a clear path & good look in on goal, which he scored with some deft hands. It's a really difficult play to defend, IMO (I've never been coached, so others can chime in), but on the initial play off the boards, Power either needs to anticipate the clear / bank-pass, or intentionally play the body and slow up Tarasenko, risk taking an interference call, and yell for his partner to play the puck and either collect the puck or hustle back to defend if there was a Blues trailer behind Tarasenko to gather it in.
Tarasenko is world class (and had a 5-point night !!!), so there's no shame in that play and goal against, but Power will need to remember nearly all the guys have speed at the NHL level and he'll need to use his body where previously his skating / stick / reach would have reduced those threats.