Jon Heyman of FanRag Sports was the first to report the deal early Thursday morning.
Piscotty is a California native, and Ahmed Fareed of NBC Sports noted the Cardinals were "looking out for him by sending him home" because his mother was diagnosed with amyotrophic lateral sclerosis earlier this year.
Cardinals manager Mike Matheny discussed trading Piscotty to support him in the wake of his mother's diagnosis, per Derrick Goold of the St. Louis Post-Dispatch:
"I don't know if I can empathize with Piscotty. You just hurt for him. You can't even really go there to understand him and at his age and what it is that he had to endure or what that is like for a family. I think it's really just understanding that it is very, very difficult. You let him know that you care. You acknowledge. You have compassion. We're trying to be support for him, and we have to look to do anything we can."
Oakland was also a natural target, considering Susan Slusser of the San Francisco Chronicle reported the Athletics were "looking for a young right-handed outfielder under long-term control." As Slusser noted, the 26-year-old Piscotty fits the criteria as someone who is signed through the 2022 campaign with a team option for 2023.
Piscotty impressed out of the gates and slashed .305/.359/.494 with seven home runs in 63 games in 2015, his first major league action. He demonstrated his power the following year with 22 long balls to go with a .273/.343/.457 slash line, but he struggled in 2017, as his numbers dipped to .235/.342/.367 with just nine home runs.
He did have his best defensive year and was responsible for eight defensive runs saved in right field, per FanGraphs.
Piscotty is still young and will be playing close to home in 2018. Oakland will look for his defensive improvements to continue as he attempts to rediscover his early form with the bat.