DeSclafani did the best in Cincinnati's all-rookie rotation during the second half of last season and was in line to start the opener at Great American Ball Park next Monday against the Phillies. Manager Bryan Price said Monday that DeSclafani has a strained oblique in his left side.
Iglesias made only 16 starts and two relief appearances last season, pitching 95 1/3 innings overall. He was 3-7 with a 4.15 ERA. He'll be the fifth pitcher in the last 20 years to start an opener with so little major league experience, according to STATS. The last Reds opening-day starter with so little experience was Frank Pastore in 1980.
Iglesias will become the first Cuban-born pitcher to start on opening day for the Reds since Adolfo Luque in 1928.
"The news the manager gave me today is the best news I've had in the last few years," Iglesias said, with trainer Tomas Vera translating.
The 26-year-old right-hander signed a seven-year deal with Cincinnati in 2014. He showed signs of being one of the Reds' best prospects last year, fanning 10 or more batters in three consecutive games in late August and early September.
He also had health problems. Iglesias was on the disabled list from June 5 to July 10 with a strained left oblique. He didn't pitch after Sept. 13 because of a tired shoulder.
DeSclafani's injury is the latest in a series of setbacks to the rotation. Homer Bailey (elbow) and John Lamb (back) are still recovering from surgery last year. Michael Lorenzen and Jon Moscot also suffered setbacks that took them out of the competition for spots during spring training.
Left-hander Brandon Finnegan is scheduled to pitch against the Phillies in the second game of the series. Price hasn't decided who will start the third game. Alfredo Simon is scheduled for April 8 against the Pittsburgh Pirates, and Iglesias is set to come back the next day.
The Reds hope DeSclafani can pitch against Pittsburgh on April 10.
Price said DeSclafani felt soreness in his side in a game against Texas on Thursday. He was examined and diagnosed with a mild strain.
"It was tolerable when I was pitching against Texas but it was getting worse every inning," DeSclafani said. "I want to be healthy all year. As much as I want to pitch opening day, the oblique can be one of those nagging injuries that last all year."
Iglesias will pitch in a minor league game on Wednesday, his final preparation for the opener.
"We want him to pitch in a controlled environment where he can get up and down six times," Price said. "We need to stretch him out to 90-95 pitches so we can reasonably expect him to pitch six innings on opening day."