Morton (5-12, 3.84 ERA) has been on the 15-day disabled list since Aug. 17 and replaces Vance Worley in the rotation, who moves to the bullpen for the final two weeks of the season. Worley is 5-3 with a 3.06 ERA in 10 starts since the All-Star break, while Morton is 0-3 with a 5.09 ERA in eight since last winning on July 2.
"He's earned an opportunity. It is what it is," Worley told MLB's official website. "I deserve a spot, too, so instead of taking me out of the equation completely, they put me in the 'pen. We'll see how things go. Hopefully (Morton) does well, because he's a reason we're here, too."
Morton has allowed 10 earned runs in eight innings over his last two starts, both losses, and last pitched Aug. 15 in a 5-4 defeat at Washington.
The right-hander has also dropped all three of his starts against the AL this season and is 1-6 with a 5.51 in nine career interleague starts. He's never faced Boston, but Allen Craig's time in the NL Central resulted in an 11-for-24 mark against Morton.
Pittsburgh (79-70), winner of eight of 10, began a six-game homestand against last-place teams by winning two of three against the Chicago Cubs, including Sunday's 7-3 victory.
Josh Harrison went 2 for 5 with a double and two RBIs and is batting .394 in his last 16 games. Neil Walker went 3 for 4 with a home run and has a .372 average over 11 games. It was his 20th home run of the season to pass Bill Mazeroski's 1958 mark for the best single-season total by a Pittsburgh second baseman.
The infield pair will try to extend their success against Anthony Ranaudo, who has been victimized by the home run in five big-league starts. Ranaudo (3-2, 5.40) has surrendered eight homers - at least one in each game - and three in last Tuesday's 4-1 loss to Baltimore.
The right-hander gave up four runs and six hits in 3 1-3 innings for his second straight loss after winning his first three major league starts.
"Any kind of pitcher that deals with a lot of fly-ball outs - like I said, here and there, you have to pick your spots when you're up in the zone, stuff like that. Today I wasn't doing that," said Ranaudo, who is also issuing 4.05 walks per nine innings, which has contributed to 11 of the 16 runs he's allowed to score via home run. "The pitches that went out of the park weren't by choice as far as being up in the zone and missing my spots. So I've gotta do a better job of that."
The Red Sox (66-84) are in a stretch of six straight series with playoff-contending teams and played the role of spoiler quite well by winning three of four in Kansas City.
They earned Sunday's 8-4 victory with David Ortiz leaving in the seventh inning due to a family emergency. Manager John Farrell said the designated hitter would join the team in Pittsburgh.
Pittsburgh's Starling Marte could be nearing a return to the lineup after entering Sunday's game as a pinch hitter. The left fielder struck out, but had hit. 390 during a 10-game hitting streak prior to being hit by a pitch on the elbow on Thursday.
Fellow outfielder Andrew McCutchen is batting .396 in 13 games versus the AL.