The skate went well because shortly thereafter he was listed as active for Game 5.
Backes has been out since taking a hard hit to the head from Brent Seabrook at the tail end of Game 2 less than a week ago. That hit resulted in a three-game suspension for the Blackhawks defenseman -- Game 5 is his last game of the suspension -- while it presumably resulted in a concussion for Backes (the Blues never said as much).
That's a huge boost for the Blues as they look to stem the tide of back-to-back losses in Chicago to even the series. Backes missed some time at the end of the regular season too and in the last five games without him the Blues have gone 0-5 with only five goals scored. Either he means a lot to his team as the captain or that's a big coincidence (it's not).
Backes was one of the Blues' leading scorers this season as well as being an important two-way player for the Blues. He plays in all situations, is one of the league's biggest hitters despite the fact that St. Louis has the puck so much and plays the role of leader.