September 14, 1976, the skinny righthander made baseball history by becoming the first Nicaraguan-born player in MLB. It was a baptism by fire, as Earl Weaver summoned Dennis from the bullpen with one out in the fourth inning and runners on first and second. The visiting Tigers had bolted out to a 6-0 lead in the first 3 innings against Ross Grimsley and Dave Pagan, but the O's came right back with 5 runs in the bottom of the third; Doug DeCinces' 3-run homer was the key blow. With the Birds having new life, Weaver didn't hesitate to yank Pagan after Alex Johnson's single bumped the score to 7-5. The 21-year-old Martinez announced himself with back-to-back strikeouts of Mickey Stanley and Bill Freehan to strand both inherited runners.
Baltimore's rookie pitcher looked like a veteran, as he scattered four hits and a walk in five and two-thirds shutout innings, sparing the rest of the bullpen. But Detroit reliever Dave Lemanczyk also quieted the O's bats after the DeCinces blast, keeping them off the board in the middle innings. The Orioles finally woke back up in the bottom of the seventh, with back-to-back doubles by Reggie Jackson and Lee May chasing Lemanczyk. New Tiger hurler John Hiller couldn't blunt the rally, as Ken Singleton coaxed a walk and DeCinces bunted for a hit to load the bases. Brooks Robinson, batting for first baseman Tony Muser, tied the game with a run-scoring groundout, and Mark Belanger drove in the winning run with a sacrifice fly to right fielder Rusty Staub. Staub's wild throw from foul territory allowed DeCinces to score an insurance run.
Martinez seized the opportunity to earn his first career win by tossing a perfect ninth inning, coaxing three straight ground ball outs. The O's were victorious by a 9-7 margin, their sixth win in a row and the first of 245 wins in the remarkable 23-year major league journey of "El Presidente".