Castillo met with the Mets' training staff Sunday in an effort to find an orthopedic insert that will limit his discomfort.
"I've been using one, but it doesn't do anything," said Castillo, who was sporting an insert in his left sandal after the game. "So we'll try something better."
Despite the pain, Castillo entered Sunday's game as a defensive replacement after manager Jerry Manuel pinch-hit for second baseman Alex Cora in the seventh. Castillo singled in his lone at-bat and reported a fair bit of discomfort after the game.
He entered only because the Mets had no other viable middle-infield options.
"We didn't have any more players, man," Castillo said. "And I play for the team."
Though Castillo can trace the roots of his injury back to Spring Training, he aggravated it by making a hard turn around first base in the seventh inning Saturday. Castillo remains day-to-day.
"I've had this for a long time," Castillo said. "Some days I feel good. Some days I feel worse."
Manuel believes the injury is a byproduct of the knee troubles that have dogged Castillo in recent years. Castillo had right knee surgery following the 2007 season.
"He's had some issues with his knee, and that's probably something that has taken its toll over time," Manuel said. "You try to protect one area and you hurt something else."