The right-hander Iglesias is 1-0 with a 3.94 ERA in four appearances, including two starts.
Reds manager Bryan Price said he doesn't believe Cueto's stiffness is a serious issue, but wants to give the pitcher an extra day or two between starts. Cueto is 3-4 with a 3.03 ERA in nine starts.
"I've asked a lot of Johnny — he's been our workhorse — so if he needs a little rest, he certainly has earned it," Price said. "We'll just plug him in whenever he's ready."
Cueto was 20-9 with a 2.25 ERA and finished second in the NL Cy Young voting last season. He led the league with 34 starts, 243 2-3 innings pitched and 242 strikeouts. Cueto also made the All-Star team for the first time.
Catcher Devin Mesoraco has been sidelined again with a hip injury. He experienced increased pain in his left hip Friday while attempting catching drills.
Price said a decision to place Mesoraco on the disabled list "is pending because he's not doing very well."
He hasn't caught a game since April 12 and will be examined by team doctors when the Reds return to Cincinnati on Monday.
"Yesterday didn't go well and my hip doesn't feel good," said Mesoraco, who is batting .178 with two RBIs in 45 at-bats. "It's upsetting because I expected to feel better by now, but it feels like it did at the beginning when I got hurt."
Mesoraco has made four starts — all at designated hitter — and 13 pinch-hitting appearances since being injured.
He also made the All-Star team for the first time last season when he batted .273 and led NL catchers with 25 homers and 80 RBIs.
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