Halladay was dealing with issues from the stifling heat. While the temperature at first pitch was recorded at 91 degrees, it felt much hotter with the heat index reportedly approaching 105 degrees.
Halladay, who was examined by the Cubs' physician, was unavailable for comment after the game, but he told a team spokesman that he "absolutely" plans to make his next start. The Phillies return to Citizens Bank Park this weekend, where Halladay is scheduled to face the Padres on Saturday.
Halladay labored through a strenuous third inning, when he threw 31 pitches and allowed two runs.
"You could tell the heat was getting to him a little bit," pitching coach Rich Dubee said. "I talked to him after the fourth, and he said he was somewhat lightheaded, but he wanted to go back out there."
He later allowed a leadoff single to Starlin Castro in the fifth, then took Aramis Ramirez to a 1-1 count before exiting. He finished with seven hits and three earned runs in four-plus innings.
Halladay put his hands on his knees as Dubee made his way to the mound. Head athletic trainer Scott Sheridan followed Dubee to the mound. After a brief discussion, Halladay and Sheridan left the mound and returned to the visitors' clubhouse.
It was Halladay's shortest outing since June 12, 2009, when he pitched three innings against the Marlins. But that was because he suffered a groin injury, which led to a trip on the disabled list. It also snapped a streak of 63 consecutive starts of six or more innings on the road. It was the longest streak in the big leagues since Walter Johnson had 82 consecutive starts of six or more innings on the road from 1911-15.
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.