Pineda (6-2) tossed seven scoreless frames, yielding only a pair of hits and a walk. He struck out nine.
Combined with his previous start Monday against Minnesota, the rookie right-hander has yielded five hits over 14 shutout innings with 16 strikeouts.
Mike Wilson drove in runs with a single and a double and Jack Wilson added two hits and an RBI for the Mariners.
Clayton Richard (2-5) gave up three runs on seven hits in a five-inning start for the Padres.
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