Aaron Boone says Luis Severino's rehab outing 'went really well'Severino had pitching day pushed after feeling back stiffness on Wednesday5/13/2021, 9:31 PMCoby GreenFreelance Editorial ProducerFeb 13, 2020; Tampa, Florida, USA; New York Yankees starting pitcher Luis Severino (40) throws a bullpen session during spring training at George M. Steinbrenner Field. Mandatory Credit: Kim Klement-USA TODAY Sports / Kim Klement-USA TODAY Sports