After a costly gamble that Blues general manager Doug Armstrong said he’d take again, the club is saying goodbye to goaltender Ryan Miller after just 25 games. The Blues announced the signing of Brian Elliott on Monday to a three-year, $7.5 million contract extension, signaling the end of Miller’s time here. The club had already advertised the arrival of prospect Jake Allen on a full-time basis in 2014-15. “Brian will team up next year with Jake Allen to provide our goaltending tandem,” Armstrong said. “We’re looking forward to those two guys competing and performing well.” This is a decisive turn of events considering the size of the package the Blues sent to Buffalo to acquire Miller and that the club made “overtures” to re-sign the pending unrestricted free agent beyond the 2013-14 season. On Feb. 28, the Blues sent the Sabres goalie Jaroslav Halak, forward Chris Stewart, prospect William Carrier, a first-round pick in 2015 and a third-round pick in 2016 in exchange for Miller and forward Steve Ott. The move was well-endorsed around the NHL, but the movie played out much differently from the script. Miller posted a record of 10-8-1 with a 2.47 goals-against average and a .903 save percentage in 19 regular-season games, followed by a 2-4 mark with a 2.70 GAA and .897 save percentage in six playoff games, as the Blues were ousted by Chicago in the first round. “We certainly gave up quite a bit to get Ryan,” Armstrong said. “We felt as an organization that might be a piece that could push us deep and get us into the Stanley Cup and win us a Stanley Cup — that’s why the trade was made. It didn’t work out that way, obviously. “If they work, you’re hailed as a genius and if they don’t work, you’re a dummy. We took a swing ... and at the end of the day, we didn’t accomplish as an organization what we needed to.” The Blues did express interest in re-signing Miller before the playoffs, discussions that the goalie acknowledged but labeled not “very serious.” It’s believed that specific contract figures were never discussed, but the club was under the assumption that Miller, who will be 34 on July 17, would be seeking $5 million a season, if not more.