"I started off the year a little shaky with the Pirates and it felt really good to get to a new organization," Irwin said. "It's just my job to go out there and compete, and see if I can succeed. I think I've done that, and here we are."
Rangers general manager Jon Daniels said with the All-Star break ahead, Martinez will only miss two starts. He added he's been impressed with Irwin, who is 4-1 with a 2.41 ERA in Round Rock.
"Irwin's been throwing the ball really well at Triple-A," Daniels said. "Has got a very good curveball, looking forward to seeing what he's got."
Grace Raynor is an associate reporter for MLB.com.