The sun was strong during an afternoon matinee in Oakland Saturday -- which eventually ended with an 8-3 Athletics win over the Royals. So strong, in fact, that it caused two "hits" on what would have normally been easy outs.
Even with sunglasses on (in Donaldson's case) and trying to block the sun with one's glove, if the ball is right in the middle of the sun on a high sky like that, it's impossible for the defender to see the ball. It might seem a bit embarrassing, but you can't catch what you can't see. I'm sure some will point to Butler's defensive acumen (or lack thereof), but note that Donaldson is an excellent defender and had to bail on his chance.