Read this on GM; thanks to the poster Yolita. If this is true then it all makes sense as I have never seen him tank a match like he did the second set.
Miami R2: Tobias Kamke def. Del Potro 7-6(5) 6-1
These are tweets by Guillermo Salatino, an Argentinian tennis commentator.
Termino el partido fue conf a los 5' y voló a Tandil. Problemas familiares. Que se resuelvan, Delpo
Nos pidieron no ahondar en el tema pero explica el #2 set en donde Delpo estuvo desconocido. No quiso usarlo como excusa,nos dijeron
He finished the match, went to his presser 5 minutes later and flew to Tandil. Family problems. I hope they get solved, Delpo.
We were asked not to dwell on the subject but it explains the second set, where Delpo was unrecognisable. We were told that he didn't want to use this as an excuse.