With the opener of the American League Division Series tied 1-1 in the eighth, Martin clubbed a 2-0 fastball from Orioles closer Jim Johnson (0-1) into the left-field stands.
CC Sabathia (1-0) earned the victory, meting out two runs on eight hits through 8 2/3 innings as AL East champion New York grabbed a 1-0 lead in the best-of-five ALDS.
Nate McLouth drove in both runs for AL wild card-winner Baltimore.
The start of the game was delayed 2 1/2 hours by rain.
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