Pretty much this. You can't walk the bases loaded and then not expect bad things to happen. Estrada's homeruns allowed weren't a big issue until the last few, because suddenly he's walking guys. Of the first 17 homers he allowed this year, 13 were solo shots, and 4 had one runner on. The last 3 were a 2 run homer, a 3 run homer, and a granny. You can't walk guys AND be a flyball pitcher.