Of the three, Ross is the most likely to be ready. There remains an outside chance Hermida could be back, and Rabelo is the long shot of the group.
"With [Ross], I'm a little more optimistic than Rabelo," manager Fredi Gonzalez said.
Ross is recovering from a bone bruise to the left side of his knee. The incident happened last Friday at Kissimmee. Initially, it was called a hyper-extended knee, but an MRI revealed the bone bruise.
Ross is expected to platoon in center field with left-handed hitting Alejandro De Aza.
With the Mets starting Johan Santana on Opening Day, Ross is the likely choice to start in center field because he hits lefty pitching so effectively.
A year ago, Ross batted .385 against left-handers. For his career, he is a .301 hitter while facing southpaws, compared to .238 while taking on right-handers.
Hermida has been out since March 15 with a tight left hamstring. If he isn't ready for the opener, manager Fredi Gonzalez said on Wednesday that he likely would go with 40-year-old Luis Gonzalez in right field.
If so, the veteran outfielder would be making his 18th straight Opening Day start.
There is a chance Hermida could play in a Minor League game as soon as Thursday.
Rabelo went down with a sprained left knee on March 13. A switch-hitter, Rabelo is catching in the bullpen, but he hasn't played in game situations since getting his leg crashed into at home plate in a collision with Washington's Austin Kearns.
When Rabelo and Hermida are ready to play again, they will start off by seeing action in Minor League games. By doing that, if both need to open the year on the disabled list, they could be retroactive to March 21. Under that scenario, the earliest they could be activated is April 5.