KEMBA WALKER IS watching Boston Celtics teammates Marcus Smart and Jaylen Brown get up jump shots after practice, and he’s asked about what drives him to be so vocally supportive. A perplexed Walker takes a beat to answer. “I’m really just being myself,” he says. “I’m really just genuinely happy for guys and my teammates. I love when guys have success. I’ve had a lot of success in my career, and I want guys to have great success.”