The right-hander is expected to rejoin the team for Friday's game against the Nationals in Washington.
Halladay told manager Charlie Manuel and pitching coach Rich Dubee on Tuesday that he needed to leave. Halladay blew a six-run lead on Wednesday, allowing 12 hits and eight earned runs in six innings. It was just the second time in his career that Halladay allowed 12 or more hits and eight or more earned runs in a game.
The Phillies said Halladay is healthy.
Halladay's teams are 110-9 when he is spotted a four-run lead, making Wednesday a rarity.
"At times it doesn't seem like his stuff is accelerating through the hitting zone," Dubee said. "At times it does."
Dubee said that could be related to the heat, release point or other factors. He said Wednesday simply wasn't a good night for his ace. Halladay allowed six runs in the fifth inning, the first time that's happened to him since 2007.
"I think everything happened real quick," catcher Carlos Ruiz said. "I think they were sitting on pitches and they didn't miss. They were aggressive early. Then they slowed down. They had a very good idea at home plate."