Lyles, 22, was set to begin the season in the Astros' starting rotation, but he was sent to Triple-A following a poor spring. He went 2-2 with a 5.32 ERA in six games (five starts) for the RedHawks, throwing a strong game Saturday in which he allowed three hits and one run in five innings.
"This is a guy that we expected to be a part of the rotation," Porter said. "He didn't fair too well this spring, but sometimes guys taking a step back allows him to take three steps forward, and we hope that's the case with Jordan."
Porter said RedHawks manager Tony DeFrancesco had good things to say about Lyles.
"We received outstanding reports, and Tony has raved about his preparation, his demeanor and wanting to get back to the big leagues, and he's done everything we've asked him to do, and we look forward to getting him back here," Porter said.
Porter said Lyles had done a better job attacking hitters and pitching ahead in the count with improved breaking stuff. Lyles made 25 starts for the Astros last year and went 5-12 with a 5.09 ERA.
"This guy has all the skill sets to be a front-of-the-rotation starter in this league," he said. "We're hoping that is the case and the step he took back this spring added motivation to never take it for granted, to give everything he has to not only be in the big leagues, but be an elite pitcher in the big leagues."
The Astros will also add left-hander Dallas Keuchel from Oklahoma City on Thursday.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.