"I felt invisible," Headley said.
That's why the Padres' third baseman -- who will miss most of the opening month with a fractured tip of his left thumb -- said he will be more conscious of injured teammates moving forward.
"It completely changed the way I treat other guys on the DL," Headley said on Monday. "It's not that I completely ignored them. But you realize when you're on the DL how much it helps when a guy says hello to you or asks you how you're doing.
"I'm trying to be sensitive to the fact that when guys are on the DL, you don't want them to feel like I felt."
Headley said he specifically asked if he could be on this season-opening road trip, because he wanted to maintain a connection with his teammates and coaches.
"I want to be there for the guys and do as much as I possibly can to help. I want to feel like I'm part of the team and am a part of Opening Day," Headley said.
Two weeks removed from injuring his thumb sliding into second base in a game in Arizona, Headley has had one X-ray on the thumb and will likely get another on April 8, when the team returns to San Diego.
"It will be three weeks, and they say between three and four weeks is when I can expect to see some healing," Headley said.
To this point, Headley has been able to lift weights, take one-handed-hitting drills in the batting cage and cardiovascular work, the third baseman actually took some ground balls before Monday's game against the Mets -- sort of.
Using a left-handed first baseman's glove, Headley took soft ground balls before the game with his left hand -- he's wearing a splint on his thumb -- wrapped around his back. The point, Headley said, is to keep his footwork sharp.
"There are a lot of things I can do," Headley said. "When I'm cleared for baseball activity, I want to hit the ground running."