​If I’m Yankees general manager Brian Cashman, I’m making sure my phone is plugged in today. I don’t want to miss the call everyone is waiting on — the one that delivers the results of Cody Bellinger’s MRI.Learning whether the slugger’s left hamstring suffered Saturday was mildly strained or significantly torn will determine how much pressure Cashman faces to bolster the lineup before the Aug. 3 trade deadline.The Yankees are already struggling offensively. They’ve scored more than five runs just twice in the past month. Even while taking two of three games against the Phillies this weekend, the Yankees batted just .204 with a .267 on-base percentage.Cashman’s obvious solution is to find another slugger before Aug. 3. The odds are long, however. The best candidate could be Minnesota’s Byron Buxton, as pointed out by NJ.com colleague Randy Miller.Buxton, a center fielder, can hit (.264 average, 25 home runs, .869 OPS this season) and is a two-time Gold Glove winner. He’d be an across-the-board upgrade over the declining Trent Grisham, whose average has dropped 22 points this month to its current .216.But Buxton has a no-trade clause. That would be the first of two hurdles the Yankees would have to overcome. The second is the Twins’ willingness to move Buxton. They’re only 3.5 games out in the wild card race and, like many clubs, are still deciding whether to be buyers or sellers. Trade activity mostly stalled this weekend for that very reason — teams haven’t made up their minds yet.As much as Cashman would like to snare Buxton or Twins catcher Ryan Jeffers, there’s a good chance the Yankees won’t get either one. If enough teams hold onto their assets, the Yankees may be unable to improve their lineup.That’s why Cashman should be thinking about a Plan B: Instead of trying to increase run production, the Yankees’ path to the World Series might have to be through run prevention.That means going after Padres closer Mason Miller. He would strengthen an already high-caliber bullpen and create a nightmare for opposing managers. Miller, whose fastball sits between 101-103 mph, would take over the ninth inning for David Bednar, who in turn could become the game’s top eighth-inning set-up man.Coupled with Brent Headrick, Fernando Cruz and Paul Blackburn, Miller would make the Yankees unbeatable with a lead after the sixth inning. Miller is 27-for-27 in save opportunities this season.“That puts a lot of pressure on the manager in the other dugout,” a scout told me this week. “The Yankees could shorten games the way they used to with (Mariano) Rivera. If you don’t get them before the sixth or seventh (inning), it’s over. It changes your entire strategy.”To land Miller, the Yankees will have to outbid the Mariners, Pirates and White Sox — all playoff contenders who need a closer. The Padres are in a commanding position. There’s no ceiling to their asking price.I’m told Cashman is willing to trade anyone ex