Adrian Beltre was intentionally walked to get to Pierzynski, but the Rangers catcher crossed up Seattle's strategy by belting a pitch deep into the right field stands for a three-run shot.
Travis Blackley (2-1), making his second start for the Rangers since being acquired from the Houston Astros, earned the win after allowing three runs on five hits over six innings.
Saunders (10-13) ended up yielding seven runs on nine hits in a seven-inning effort.
Brad Miller drove in two runs for the M's, who dropped the opener of a three-game set.
Millions of Getty images now available for free via embed tool
Aaron Carter is still in love with Hilary Duff