Chicago might rather have faced right-hander Josh Beckett, who was scratched from his scheduled start and placed on the 15-day disabled list with right shoulder inflammation. Morales is a lefty, and the Cubs are 3-14 vs. left-handed starters this season, including Saturday's 4-3 loss to Jon Lester.
Though Morales has only appeared as a reliever for the Sox, he rose through the Rockies' farm system as a starter. He started 15 games with Colorado from 2007-09.
"I'm going to try to do what I can do, I try to control what I can control, throw strikes and try to get the hitter out," Morales said.
The southpaw has pitched well out of the bullpen, appearing in 22 games with a 3.04 ERA.
"Well, he's pitched multiple innings, and he's pitched ahead in the count with quality stuff," said Red Sox manager Bobby Valentine. "We'll see if he can't give us multiple innings again with pitching ahead in the count and quality stuff [as a starter]."
Paul Maholm is scheduled to start for the Cubs. The left-hander struck out seven in his last outing, a no-decision vs. the Tigers. He's 4-5 with a 4.91 ERA this season in 12 starts.
The Cubs took the series opener, 3-0. Chicago is 14-28 at Wrigley Field this season.
Red Sox: Pedroia slumping since return
Dustin Pedroia went 0-for-5 on Saturday night and remains hitless in the series. Since returning from a torn adductor muscle in his right thumb on June 5, the second baseman is 7-for-45 (.156) with four RBIs and 10 strikeouts.
Valentine doesn't believe Pedroia's thumb injury is the reason for his recent slump, though.
"It seems not, for me. I don't know. Again, before he hurt his thumb, there wasn't a lot of results," Valentine said. "There were similar results where he hit the ball hard and the outfielder was standing there, infielder was standing there. He says it's a total non-issue. I don't know. There's no swelling, and he says it's a non-issue."
Pedroia missed six games with the injury but has played in Boston's last 11 games.
Cubs: Marmol pitching well in return to closer's role
Carlos Marmol picked up his first save since May 2 on Friday in the series opener. As long as he continues to throw strikes, he'll remain Chicago's closer.
Marmol's save on Friday didn't come easy as the Red Sox loaded the bases in the ninth. But he regrouped and got Pedroia to ground out to end the game.
"He got back in counts with his fastball and threw four, five fastballs in a row at one time," Cubs manager Dale Sveum said. "That's what you want to see, and that's why I put him back in there because it seems like he's capable of pulling it off."
Marmol did not pitch in Saturday's loss. This season, the right-hander is 1-2 with a 5.79 ERA and three saves in 23 appearances.
The Cubs' bullpen has been in flux since Marmol was removed as the closer in early May before an injury sidelined him.
The Red Sox are 9-15 in day games this season.
The Cubs have lost 23 of their last 30 games since May 15, with 13 defeats coming by one run.
Boston is 2-3 all-time at Wrigley Field.