Drafted 38th overall in June 2008, the 22-year-old Lyles made 40 major league starts over the last two seasons and was 7-20 with a 5.20 ERA in 45 games overall. The right-hander was expected to be a member of the big league rotation this year but pitched so poorly in spring training that he was sent to Triple-A Oklahoma City, where he is 2-2 with a 5.32 ERA in six outings.
"We've received outstanding reports," Porter said. "He's done everything that we've asked him to do and we look forward to getting him back here."
Porter said Lyles has "attacked hitters" in the minors and "just done a great job of getting ahead in the count."
"His breaking stuff has been tremendous. You know, this guy has all the skill sets to be a front-of-the-rotation starter in this league and we're hoping that that is the case and hoping the step that he took back in the spring is added motivation to never take it for granted and give everything that he has to not only be in the big leagues but be an elite pitcher in the big leagues," Porter said.
"I think sometimes guys taking a step back actually allows them to take three steps forward, and we're hoping that that is the case with Jordan."
Porter said a corresponding roster move will be made Thursday before the Astros open a 10-game homestand, their longest of the season.
Lyles was headed to Houston on Wednesday to rest up, Porter said.
Peacock is 1-3 with a 9.41 ERA in six games, five starts. He made his first relief appearance of the season Tuesday night against the Yankees, allowing three runs and three hits in two-thirds of an inning.