The narrow loss at Oxford was Stoke’s first match back after September’s international break, and followed back-to-back wins.
Schumacher oversaw victory against his former side Plymouth before the break, and that victory came after a thumping 5-0 Carabao Cup win against fellow Championship side Middlesbrough on 27 August.
Before being beaten by Oxford, the only other games Stoke had lost this season were against West Bromwich Albion and Watford – sides which are top and fifth in the table respectively.
Schumacher became Stoke’s sixth boss in six years when appointed as Alex Neil’s replacement, with the club three points above the relegation places at the time.
Stoke chairman John Coates described Schumacher as “one of the most exciting young coaches in the country” after his appointment, with the former Plymouth boss leading the club to a 17th-place finish, six points clear of the drop zone.
“We have a young, dynamic squad that is eager to develop and a clear vision of how to achieve success, and we hope to announce a new appointment shortly,” Walters continued.