That fatigue, combined with a decreased range of motion in Iglesias' shoulder, prompted the decision to be made on Saturday.
"There are some things we wanted him to accomplish before we would allow him to pitch again. There's just not going to be enough time," Reds manager Bryan Price said on Sunday morning.
Considering that he barely pitched at all in 2014 as he sorted out visa issues in Haiti following his defection from Cuba, Iglesias had a nice rookie year in the Majors. The 25-year-old finished 3-7 with a 4.15 ERA in 18 games, including 16 starts. In 95 1/3 innings, he allowed 81 hits and 28 walks with 104 strikeouts and a 1.14 WHIP.
Iglesias ran a streak of seven straight quality starts from Aug. 1-Sept. 2 over which he had a 2.31 ERA. During that stretch, he also became the first Reds pitcher in modern history to record at least 10 strikeouts in three consecutive starts.
"It doesn't make any sense for him to pitch the rest of the year, but he'll really focus on Spring Training," Price said.
For Marshall, it's a hard-luck outcome after he worked diligently to come back from two shoulder surgeries. In 2014, he had an operation to repair a torn labrum, and on May 20, he had a second less-invasive procedure to remove scar tissue.
Marshall had been throwing for the past couple of months, and there was hope he could appear in a game before the season ended.
"He's having a little recurring tenderness in his shoulder," Price said. "He tried to work his way through it. He's actually had some very productive bullpens. He's probably thrown over a dozen bullpens now. But he hasn't been able to get over the hump where he can go an extended period of time without some discomfort."
Marshall led the Majors with 231 appearances from 2010-12, but the shoulder problems have limited him to 31 games pitched since 2013. He made $6.5 million in '15 and will be a free agent this winter.
• The Reds claimed outfielder Tyler Holt off waivers on Sunday and moved utility player Kristopher Negron to the 60-day disabled list. Holt, 26, was 2-for-20 (.100) in nine big league games this season for the Indians, who designated him for assignment last week. He hit .302 with no home runs, 28 RBIs and 25 stolen bases in 101 games with Triple-A Columbus.