Alexander Frolov’s season — in which he tallied a disappointing seven goals and nine assists — is over after the winger tore the ACL and meniscus in his right knee and sprained his MCL in a collision with the Blues’ Brad Winchester on Saturday night. In a perfect world, Frolov would have provided a second scoring threat on a top line with Marian Gaborik this season. Instead, he’d been demoted all the way to the fourth line when he sustained his season-ending injury. (Still, in the Post, Larry Brooks makes the case that John Tortorella could at least trust Frolov — who will be replaced on the roster by Kris Newbury — in any situation, including ones late in tight games.) The Rangers won that game against St. Louis, by the way, as well as the one in Dallas the night before. (Some of those encouraging stats from our mid-season report look even better now: They won yet another game on Friday in which they trailed after two periods, they remained undefeated in games in which they’ve led after two with the win on Saturday, and they extended their current winning streak to three games.) They’ll next play Montreal tomorrow night at the Garden.