The fact the losing pitcher was the closest thing the Mets had to a bright spot yesterday shows just how things are going in Flushing these days. Jon Niese was betrayed by a struggling lineup, shaky defense and sorry bullpen, all culpable in a 5-1 loss to Philadelphia that ran the Mets’ season-high losing streak to four. Want to put a number on their misery? Three: As in getting held to only three hits, making three errors and mustering just three wins in a nine-game homestand. Want to put an image to their malaise? Try John Buck’s two-out error in the seventh, which opened the door for Ryan Howard’s two-run double off Scott Atchison that broke a 1-1 tie — and the Mets’ collective backs. Niese matched Cole Hamels (1-3) in a pitchers’ duel until giving up two-out singles to pinch-hitter Laynce Nix and Jimmy Rollins in the seventh. When manager Terry Collins went to the righty Atchison, Phillies manager brought Howard off the bench. And when Atchison fell behind 2-0 and had to challenge Howard, the slugger drilled a 92 mph cutter off the fence in center field to bring home both runners for a 3-1 lead. Chase Utley singled to left on the next pitch to make it 4-1. The way the Mets have been hitting, it might as well have been 14-1. “I was trying to make a good pitch low and away on 2-0 and I didn’t do it. I didn’t execute the pitch. I wanted to pick up Jon right there, get us out of that inning and I didn’t execute,’’ said Atchison. “I didn’t execute. I left it back over the middle. He’s a good hitter and made me pay.’’