This is anticipated to be the first of at least two waves of promotions by the Pirates, with additional moves expected at the end of the Indians' playoff run.
Holt will be making his big-league debut after sparkling in his first month at the Triple-A level. A slight (5-foot-10 and 165 pounds) Texan, he hit .432 in 24 games following his promotion from Double-A Altoona, where he hit .322 in 102 games for the Curve. A ninth-round pick in the 2009 First-Year Player Draft, Holt has a .317 career Minor League average.
Leroux will also be making his first appearance of the season with the Pirates, after having spent the first two months recovering from a strained pectoral muscle. He joined Indianapolis, first on a rehab assignment, on June 10 and was 4-0 with a 3.11 ERA in 21 games, including seven starts. The 24-year-old appeared in 51 games in 2009-11 with the Marlins and the Pirates, who selected him on waivers from Miami.
Locke, 24, was also a September callup last year, and briefly rejoined the Bucs earlier last month, allowing one hit in 4 1/3 innings of two relief appearances.
Manager Clint Hurdle is expected to choose Locke to start on Tuesday in PNC Park against the Astros, stepping into the spot vacated by released veteran lefty Erik Bedard.
Wilson, a career starter in the Minors, was recently converted to relief work, apprenticeship for the role he is expected to fill with the Pirates. In a one-day big league introduction last month, he fired a shutout inning in San Diego, striking out the side around two hits allowed.
Fryer has had brief stays with the Pirates in each of the last two seasons. Recalled in early July, he appeared in four games, primarily as a pinch-hitter.