Ethier is coming off September knee surgery that was hoped would return the power to the left-handed slugger, who dropped 12 home runs and 20 RBIs from 2010.
In addition, his batting average against left-handed pitchers has been almost in complete retreat since his first season of 2006: .351/.279/.243/.194/.233/.220.
"I'm able to keep my front side closed now," said Ethier. "Keep the hips closed rather than rotate. It's the same in golf. You need that torque. Now I can set my front leg and it results in power, knowing that I don't feel a twinge and that I don't have to second-guess myself because I have to compensate for what I can't do. Yesterday [a double] and today are from the work I did over the winter."
Manager Don Mattingly said he would be impressed with what he sees from Ethier even if he wasn't coming off surgery.
"It's amazing to me when guys can swing like that right away," said Mattingly, who was a slow starter in Spring Training as a player. "I'm always amazed to see guys just jump in and start to hit."
Mattingly said he can see a difference in Ethier's mechanics from last year.
"I see him square right now and I know his swing is going to be short," he said. "His contact points are good right now."
Mattingly said he plans to bat Ethier fourth against right-handed pitching and fifth against left-handed pitching, as he did Tuesday, when Juan Rivera hit behind Matt Kemp.