The 21-year-old right-hander allowed a run on six hits and a walk while striking out a pair over seven innings in his debut for Double-A Corpus Christi in a 4-1 loss at home against Frisco.
A product of North Carolina State University, Buchanan induced six ground-ball outs to begin the game before running into and out of trouble in the third.
Elio Sarmiento singled to right field to start the inning and Jared Bolden reached on an infield hit, but Buchanan regrouped by retiring the next three batters to keep Frisco off the board.
The 2010 eighth-rounder worked around a two-out walk to Jonathan Greene in the fourth, and he used an inning-ending double play in the fifth to erase Bolden's base hit to right field.
Buchanan was perfect in the sixth and he stranded two RoughRiders in scoring position in the seven, but he lost his shutout an inning later. David Paisano led off the eighth with a single back up the middle, forcing the right-hander out of the game after throwing 56 of his 83 pitches for strikes and recording 13 ground-ball outs.
Incoming pitcher Daniel Meszaros (0-4) allowed the next three batters to reach base as part of a four-run inning.
Buchanan is in his second year of pro ball. He was 4-5 with a 4.28 ERA in 14 starts for the Class A Short-Season Tri-City Valley Cats last year and he went 5-10 with a 3.91 ERA in 25 appearances for the Class A Advanced Lancaster JetHawks prior to his Aug. 31 promotion to Corpus Christi.
Left-hander Richard Bleier (7-8) picked up the win for the RoughRiders, tossing 2 1/3 scoreless innings. Starter Neil Ramirez surrendered a run on three hits and two walks while striking out seven over 4 2/3 frames.