Daniel Alfredsson has an enthusiasm that teammates have come to love, and rely upon. He’s a leader for them, something of a playoff linchpin, and one of the reasons the Red Wings feel good about themselves as they engage the Boston Bruins in the first round of the playoffs. Alfredsson came to Detroit last summer after 17 seasons with the Ottawa Senators because he sized up the Wings as giving him a better chance to chase a Stanley Cup in the twilight of his career. Alfredsson has no regrets, even as the Wings were roiled by injuries to superstars Pavel Datsyuk and Henrik Zetterberg, greatly altering the team Alfredsson thought he was joining. “It’s been a great year,” Alfredsson said Wednesday. “A challenging year, also, in a lot of ways, but also gratifying, I guess, with the way we battled and were able to put ourselves in the position we wanted to be in. Clinching the playoffs in Pittsburgh was a great feeling, and here we are, starting. It’s exciting. We all know how fun it is going into that first round and playing that first game.” The sheer joy of playing hockey is part of what has made Alfredsson, 41, such an elite player for nearly two decades. Even as his body has been battered — and his lower back sometimes tightens up to the point he needs to sit a game or two — Alfredsson maintains his good humor.