Making his second start since joining the Phillies, Williams (1-0) allowed one run and three hits in seven-plus innings.
Mariners rookie lefty Roenis Elias (9-10) gave up one run and three hits in four innings. He constantly pitched out of jams because he walked six and hit one batter with a pitch.
Blanco connected for a three-run shot off reliever Dominic Leone in the fifth to give the Phillies a 4-0 lead. It was his first home run since July 1, 2011, for Texas against Florida.