The Philadelphia Phillies have been waiting since MLB Spring Training for encouraging news on Aidan Miller, and the club finally shared a positive update on the prospect’s lingering back injury.President of baseball operations Dave Dombrowski told reporters, including Todd Zolecki of MLB.com, that Miller has started swinging a bat recently. “It’s just the next step in his progress,” Dombrowski said. “It’s step by step daily. I can’t tell you wha…