You do realize Estrada was selected to the All-Star team only a year ago, right? No, that guy hasn't been pitching this season, but it's not like it isn't in him to do so.
He changed speeds effectively. If you throw everything the same speed, major league hitters will catch up to it (Joe Kelly is a good example of this). Take a pitcher who can change speeds (i.e., can upset timing), facing a team that doesn't hit off-speed stuff all that well to begin with and is in a overall teamwide slump, and you've got the ingredients for a 3 hitter.
40 years ago, Randy Jones won a Cy Young and had a couple 20 win seasons throwing pitches as slow as 72 mph (and topping out at 85). There are many ways to get hitters out.