"I've never had something like that," he said.
He left Monday's 6-1 loss to the Chicago Cubs at Wrigley Field in the fifth inning because of heat exhaustion. The heat index Monday reportedly hit 103 degrees. But Halladay said Tuesday he felt better and expects to make his next start Sunday against the San Diego Padres at Citizens Bank Park.
He said he still can't explain why the heat affected him so much. He said he consumed plenty of fluids, a process he said begins the day before he pitches.
"It seemed like in between innings, I couldn't get away from it," he said. "I think it just got to the point where it just kept continuing and kept getting hotter and hotter, and I couldn't stop it. It was a combination of everything -- heat, travel -- I think it got me at one point. In that last inning, there was a point where I felt like I was about to get wheeled off the mound."
Halladay declined to say if he received an IV but said two Cubs doctors treated him after the game. He said he cut back his post-start workout Tuesday, but said it should not affect him with an extra day to prepare because of a day off Thursday.
"Tomorrow hopefully will be more of a regular day," he said. "The big thing they were concerned about was the cardio today. It was just making sure I didn't get that high rate up and everything again."