Pineda struck out seven and allowed two hits over six shutout frames Saturday before the Mariners dropped a 2-1, 10-inning decision to the Brewers in Maryvale, Ariz.
Pineda, MLB.com's No. 13 prospect, faced the minimum through three innings before running into trouble in the fourth. The 22-year-old right-hander yielded a two-out single to veteran Mark Kotsay and walked All-Star Prince Fielder, putting a runner in scoring position for the first time. Yuniesky Betancourt singled to right fielder Ryan Langerhans, who nailed Kotsay at the plate to end the inning.
Pineda, who walked two, set down the final six batters and exited a scoreless tie.
The 6-foot-7 native of the Dominican Republic solidified his candidacy for a spot in the Mariners' rotation. He lowered his ERA to 2.12 ERA in five Cactus League appearances, fanning 15 batters over 17 innings while yielding 14 hits.
Pineda was 11-4 with a 3.36 ERA in 25 starts between Double-A West Tenn and Triple-A Tacoma in 2010.
Pinch-hitter Mike Wilson doubled in the ninth for the Mariners, while Cesar Jimenez allowed a hit and struck out one in a scoreless inning. Brian Moran (0-1), a 2010 Midwest League All-Star, retired one batter and was charged with an unearned run.
Former fourth-round pick Eric Farris went 0-for-2 for the Brewers after coming on as a pinch-hitter.