"Our guys thought there was a chance that it was offside," Avalanche head coach Bednar said after the contest. "It is hard to tell, but they obviously had an angle they looked at."

The goal was reversed and despite several scoring chances by the Avs in the closing minutes, they were unable to (re)tie the game and lost its third in a row.

On Friday, the NHL announced that it had made a mistake with the call.

"The video review decision determined the play was off-side but that determination was based on a play prior to the puck clearing the zone," the league said in a release.

"Per Rule 78. 7 (Note 1) Coach's Challenge: 'Goals will only be reviewed for a potential "Off-Side" infraction if: a) the puck does not come out of the attacking zone again; or (b) all members of the attacking team do not clear the attacking zone again, between the time of the "Off-Side" play and the time the goal is scored.

"Although there was an off-side, it occurred prior to the puck clearing the zone which nullifies any goal review related to that off-side. The entry in to the zone immediately prior to the goal was on-side, therefore the goal should have counted."

Video: Jared Bednar talks injuries and offside call

So while Andrighetto was initially offside, a play that was missed by the linesmen, he was able to get onside before carrying the puck back into the attacking end, which soon resulted in a would-have-been goal by Mikko Rantanen.

Based on the rule, the Blues could have only challenged the second zone entry and not the first one that was offside.

On Friday after the team's optional practice at Family Sports Center, Bednar recognized the many issues of the challenge but was also ready to move on from it.

"I think there are two things there. I appreciate them coming out and saying that," said Bednar when asked about the league admitting it had made a mistake. "The original play was clearly offside and probably should have been whistled before the entry we scored on. I think at the end of the day the right [outcome] was made if you use common sense.

"The way the rule sits, the (second) entry was a good entry and the goal could have counted. It was a mistake, and our focus is more on our team game and how we can play and we can't worry about decisions like that. They're doing their best to get the call right on the ice."

Thursday was a learning experience for everyone involved. Not just for the Avalanche, Blues, on-ice officials and the league, but the other 29 NHL clubs as well.

Bednar said his coaching staff looks at every coach's challenge around the league to get a better feel for what is and isn't allowed so they can make an educated decision in the heat of a game.

"We're trying to get real clear on all those calls so we know when to challenge and when not to challenge, and hopefully get it right more times than not," Bednar said. "We learned from last night's call, for sure."

Offside challenges are more high skates this year because of a rule change in the offseason.

In past years, if a team lost its challenge, either for offside or goaltender interference, it would also lose its only timeout. That is still the case this season for interference calls, but lost offside challenges now result in a delay of game penalty for the club that contested the call.