Walker stayed in through the eighth inning but was removed in favor of pinch-hitter Matt Reynolds in the top of the ninth.
"When you get a ball kind of close to your heart and kind of close to your rib cage there, you just want to make sure," Walker said. "I didn't want to go out there and dive and do something to aggravate it more if there was something going on. [The doctor] didn't see any issues and didn't think an X-ray was necessary, so we'll play it day by day."
A former catcher, Walker admitted that his catching instincts took over and forced him to try to smother the ball.
"You have two choices -- you can try to side-saddle it, or you try to chest it up," he said. "My first reaction was to try to keep it in front of me at any chance. You hope it hits you in the gut and you have enough meat there to soften it, but that wasn't the case."
With three regulars already on the disabled list, the Mets can ill afford to lose another bat. However, it appears as though Walker avoided serious injury.
"I feel OK now, but I was a little lightheaded and didn't feel quite [right] for a few minutes, so I thought it was best to shut it down for the day," he said.
Andrew Gruman is a contributor to MLB.com and covered the Mets on Tuesday. This story was not subject to the approval of Major League Baseball or its clubs.