Starting the backup tonight in no way means they aren't treating this as a playoff game. Being in the hunt this late in the year, they are all playoff games until they are in or out. Tarasov is going to get some games between now and the end of the season, and the Jackets are going to lose some games between now and then, just how it is going to be. For all anyone knows, Elvis could just have some soreness and they are giving him an extra day.
Giving the backup some games isn't the big deal people are making it. The team just needs to play their game, and things will fall into place, tonight isn't make or break. There are still 23 games after tonight.