Smith, who earned his third promotion to San Diego in two months, hopes to improve on his previous performance in the Majors. He will join the bullpen as a long reliever.
"Burch is going to help supplement our bullpen," manager Bud Black said. "He gives us another arm that has some length to it."
"It's always good to be up here," Smith said of his return to the Majors. "It's definitely where you want to be."
Smith was first recalled from Tucson on May 11 and struggled in three starts, posting an 0-1 record with an 18.41 ERA in 7 1/3 innings. He was optioned back to Tucson on May 22.
The Padres again recalled Smith on June 8, but the 23-year-old did not make an appearance for San Diego before he was optioned back to Triple-A on June 10.
"I tried to tone it a little bit more maybe in the first inning instead of trying to throw the ball as hard as I can," Smith said of what he worked on in the Minors. "Just relax and try to pitch a little bit more and save that for an out pitch or focus more on location."
Smith began the season on a high note at Double-A San Antonio, where he was named the Padres' Minor League Pitcher of the Month in April after compiling a 1.38 ERA in five starts.
Layne returns to Tucson, where the 28-year-old is 1-3 with a 4.03 ERA in 24 appearances.
Joe Morgan is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.