The Red Sox pitcher fanned a career-high nine hitters, allowing two runs on four hits in five innings without walking a batter, in his first start since April 21, 2009. He started for Josh Beckett, who was placed on 15-day disabled list with shoulder inflammation.
"I felt very strong today and I could go one more inning, but that's not my decision," Morales said. "I know it's been a long time since I've thrown a lot of pitches."
Despite leaving with a one-run lead after a solid performance in his first career Interleague start, Morales didn't get a decision in the 7-4 Red Sox win. The Cubs took advantage of two Red Sox errors to tie the game at 3 off reliever Matt Albers in the sixth.
Morales still pitched well enough that manager Bobby Valentine said he'll get another start and will likely throw more than the 80 pitches he tossed Sunday.
"He performed well in that situation and he proved our hunch correct," Valentine said. "Those were five pretty good innings, and he had more, according to him. I'd like to give him a chance to do well next time."
Cubs manager Dale Sveum said Morales didn't need to use a full repertoire to get his hitters out.
"We were getting beat constantly on the fastball," Sveum said. "That's the bottom line. It wasn't like he was doing a whole lot else besides throwing a lot of fastballs."
Morales, who was 0-1 with a 3.04 ERA as a reliever this season, allowed just two hits in 7 1/3 scoreless innings in his previous two relief appearances, which was enough to show Valentine he could still pitch well in long spurts.
"I think we might have mentioned that at the time," Valentine said. "You always have to try to plan and work on the next thing."
Morales capped a performance that Valentine called "spectacular" by belting his first hit in three years.
"I tried to make [Cubs starter Paul Maholm] throw more pitches to me, and I tried to stay back with the curveball," Morales said.
Rowan Kavner is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.