Martinez, who was on call as the Rangers' long man on Thursday, will go back into the Round Rock rotation and start on Friday night.
To make room for Faulkner on the 40-man roster, the Rangers designated left-hander Chris Rearick for assignment two days after claiming him off waivers from the Padres.
"Martinez was just here to give us protection," manager Jeff Banister said. "Faulkner was one of the guys we saw in Spring Training who threw the ball well for us. We liked what we saw. He has good action on his fastball, a swing-and-miss breaking ball and has been getting better ever since. He is a guy we had on the radar all year. He has made progress and forced us to get him in the mix."
Faulkner began the season as a starter at Double-A Frisco but has flourished since moving to the bullpen.
"It has been way different," Faulkner said. "I haven't had too much time in the bullpen, but it looks like I've adjusted well. It has been a fun ride."
Faulkner was moved to the bullpen on July 10 while with Frisco and had a 0.40 ERA over his last 18 relief appearances, holding opponents to a .072 batting average with 28 strikeouts in that span. He also has a 19 2/3-inning scoreless streak over his last 16 outings at the Minor League level.
Faulkner was promoted to Round Rock on Aug. 12 and threw eight scoreless innings with 13 strikeouts over his first six relief appearances. He has held Pacific Coast League batters to a .080 average, with left-handed batters going 0-for-9 with seven strikeouts.
The Rangers now have three left-handed relievers in Faulkner, Jake Diekman and Sam Freeman.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.