At the risk of turning this Red Sox season into an extended Kumbaya singalong and cookie party, last night brought another encouraging sign of unity. It’s no stretch to say the Sox are playing their best baseball since August 2011, and even though many fans roll their eyes at the mention of chemistry, we’d like to focus on one moment in last night’s 7-4 victory against the Yankees. It came in the third inning with the Red Sox leading 3-0. Shane Victorino delivered a two-out RBI single and stole second. Newcomer Jackie Bradley Jr. stepped to the plate, worked the count to 2-2 and drilled a Cody Eppley sinker straight up the middle and into center for his first big league hit. Victorino, who was running on contact, scored easily. But before returning to the dugout, he turned to first and signaled for the ball, recognizing the personal significance of the moment. The youngster touched the bill of his cap in appreciation. “I was just asking for the ball,” Victorino said. “Wanted to make sure we got him that ball. That’s a big moment, his first hit. I wanted that ball for him.” The ball ended up in a sock in Bradley’s locker, much to the rookie’s delight and surprise. “It just snuck up there,” he said, noticing the memento only after having it pointed out by reporters. Bradley carried himself marvelously since the start of spring training, exhibiting confidence without cockiness and treating the team’s veterans with respect while focusing singularly on winning a job. The Red Sox face a numbers game when David Ortiz returns, and it would be easy for the team’s veterans to freeze out Bradley, since the only way he’ll stay in the big leagues at that point is by taking a starting outfield job from either Jonny Gomes or Victorino. “Whatever they have in the plans for the future with me, you know I’m all for,” Bradley said. “I’m just trying to help the team out while I’m here.”