Depends how you interpret my statement. What I mean is that when a ground ball pitcher has good luck it might be of more benefit to him than a high HR pitcher like Estrada. Conversely, when they have bad luck it might do them more harm.
Let's take a sample size of 2 balls hit in play. Let's say in one game Sanchez has 2 ground balls hit hard directly at Josh Donaldson, as opposed to directly down the left field line. Both of those balls would likely be outs instead of base hits based purely on luck as Sanchez has no real control as to whether they are hit at Donaldson or down the line. Let's say in another game Estrada allows 2 home run balls hit directly over Josh Donaldson instead of directly down the first base line. There will be no benefit to Estrada in this case.
Let's take another game where Sanchez has 2 hard ground balls hit directly down the third base line instead of directly at Donaldson. In this case the exact opposite happens. Over the course of a season, or a career, things will even out, but in a small sample size, Sanchez might benefit more from good luck than a pitcher such as Estrada. Obviously there will be a lot more at bats in these games, but even a few at bats in a game can have a large impact on the result. I'm not saying that this is what's happened here, but I believe that it is a possibility, and might in part explain part of what has happened with Sanchez this season.