Cora got the starting nod over Castillo at second base on Monday against San Diego right-hander Kevin Correia.
"I'm going to probably go that way until Luis starts moving a little bit better on that foot," said Mets manager Jerry Manuel.
If the Mets face several right-handed starters in a row, the switch-hitting Castillo is likely to play against some of them, and he should continue to start regularly against lefties.
But against most right-handed starters, Castillo will sit.
The goal is to provide him with regular rest in the hopes that the nagging bone bruise in his left foot might finally heal.
Though Castillo downplayed the severity of his injury prior to Monday's game, Manuel said that by favoring his right side, Castillo has now caused some discomfort in that foot as well.
It is still possible that the veteran may require a disabled-list stint sometime in the near future.
"We have to keep doing what we're doing, and if it doesn't get any better, then we have to make a decision which way we're going to go," Manuel said. "[If we] decide, 'Hey, this is not benefiting him and it's not benefiting us,' then we have to give him rest, put him on the DL."