The minor leaguers were not identified.
He signed a $33.5 million, six-year contract extension in the offseason that runs through 2022.
Throughout the season, Piscotty was struggling at the plate only batting.235, hitting nine home runs and having thirty-nine runs batted in while having 341 at-bats.
Both numbers were significantly down from 2016, when he hit.273 with 22 home runs.
Indian cricketer Ajinkya Rahane's father booked for negligent driving
The vehicle he was driving ran down a 67-year-old woman in Kohlapur, who later succumbed to her fatal injuries in hospital. The middle-order batsman is scheduled to leave with the rest of the team for a tour of South Africa later this month.
"It was time to get back and spend time with her", Piscotty said. "You just hurt for him". "I think it's really just understanding that it's very, very hard". Piscotty returned to the lineup after about a week away.
The A's traded Ryon Healy to the Mariners partly to open the DH spot for Khris Davis, who has defensive deficiencies as a left fielder but has produced more than 40 homers and 100 RBI each of the last two seasons.
The A's had been interested in Piscotty for some time and were willing to part with Munoz and Schrock - their No. 13 and No. 17 prospects, respectively, according to MLB.com - because they have a deep reservoir of young infielders in the minors.
Piscotty's time in St. Louis will surely never go unforgotten as he has made a name for himself in baseball, has helped the Cardinals to many victories and touched the hearts of many Cardinals fans.
The trade also brings the 26-year-old Bay Area native and Stanford star closer to home. Classy move by the Cardinals.