Stephen was among the many family members who surrounded her during her final moments Sunday evening, a debilitating disease taking her far too soon. She is also survived by her husband, Michael, and sons, Nick and Austin.
"Obviously the organization, certainly the players, we have heavy hearts for him," A's manager Bob Melvin said. "We know what he's been going through, and he's been going through it for quite a while now. We really feel bad for him. He's really close to his mom."
The Cardinals facilitated a trade with the A's in December to bring Piscotty closer to his hometown of Pleasanton, Calif., and he's since spent the majority of his time away from the ballpark caring for her in the family's home.
He was understandably absent from the Coliseum on Monday and will likely be placed on the bereavement list following the A's homestand, Melvin said.
"There's real life, and then there's what we do, which is basically the entertainment business," he said. "That's a real-life situation, and we all feel bad for him."
Condolences came pouring in elsewhere, too, including heartfelt messages from the Cardinals.
St. Louis manager Mike Matheny called Gretchen "a first-class lady."
"I got to spend some time with them, knowing Stephen from the Draft all the way through," Matheny said. "It's been a tough go for them. I'm thinking about and praying for their family.
"Understand that as much of a façade guys put on, life happens. A lot of the things people know about. A lot they don't. You can't put a template on how to go through that or how to handle it, but Stephen is a first-class guy himself. Great family, and we're hurting for them all the way through."
In a statement issued by the team, A's executive vice president of baseball operations Billy Beane said, "The Athletics organization extends its deepest condolences to the Piscotty family on the loss of Gretchen. She was a devoted wife and mother, whose legacy will live on through her husband, Mike, and their sons, Stephen, Austin and Nick."
The A's are matching up to $50,000 of memorial contributions made to the ALS Therapy Development Institute via youcaring.com/piscotty.
Cubs pitcher Yu Darvish, despite not knowing Stephen personally, extended his support of the Piscotty family through a $10,000 donation and tweeted, "We are all family :)"
Good friend and former Cardinals teammate Randal Grichuk also tweeted his condolences.
St. Louis president of baseball operations John Mozeliak relayed his thoughts in a statement:
"From the moment we drafted and signed Stephen, he and his family became a part of the Cardinal family. We were saddened to hear of the passing of Gretchen and want to let Stephen and his family know that we pass on our heartfelt condolences."
In Oakland for Monday night's game, Astros manager A.J. Hinch said, "I'm grateful that baseball found a way to bring his family together. I don't know him personally. I met him at Stanford a couple times. I was glad he was able to spend her last moments helping."
Jane Lee has covered the A's for MLB.com since 2010.