The juggernaut of consistency, the depth of solid efforts, the foundation of discipline — it all seems to be seeping away from the Rangers early in this shortened season, as they flail and grasp at any stray point they can get their hands on. Last night was an up-and-down performance from a team that was undermined by both injury and poor play, and the result was a 3-2 shootout loss to the Senators at Scotiabank Place. “I’m glad we got a point,” coach John Tortorella said. “I just don’t think our whole lineup is playing. We just have to keep grinding away until we get people playing and try to grab points when we can.” It was looking to be a gutsy if unartistic comeback performance for the Rangers (8-6-2) when Ryan Callahan and Ryan McDonagh scored 51 seconds apart midway through the third period to give the Blueshirts a 2-1 lead. The Senators (10-6-2) had already replaced their starting goalie Craig Anderson — who was terrific in making 21 saves — with backup Ben Bishop early in the period after Anderson was slammed into by a sliding Chris Kreider, the result of an unpenalized trip from behind by Marc Methot. So, with the lead in hand the Rangers, playing for the second straight game without superstar forward Rick Nash (undisclosed injury), would have been best off settling down and defending. The Rangers’ road to the Eastern Conference finals last season went through a seven-game series against this Senators team, so holding on for a close win seemed to be something they could do by drawing from their past. Instead, the misdeeds continued, this time in the form of a Brian Boyle holding call and the subsequent (and predictable) equalizer from Mika Zibanejad with 6:30 remaining. “I thought we were up and down a little bit,” said Callahan, whose fourth goal of the season came on a power play, when he buried the puck after a bounce off the back wall from a Marc Staal slap shot. “That’s the way this game works, you get in penalty trouble and it’s tied 2-2.” The 4-on-4 overtime saw some chances for both teams, and none was more precious than when Marian Gaborik — playing his most assertive game in weeks — got his own rebound and rang the crossbar loud enough to resonate in the team’s psyche all the way to Montreal, where they will play tomorrow night.