7-inning doubleheaders, 26-man rosters among rules included for 2021 MLB seasonFrequent PCR testing, mental health resources among safety protocols2/9/2021, 8:02 PMCoby GreenFreelance Editorial ProducerJun 21, 2017; Kansas City, MO, USA; Major League Baseball Player Association executive director Tony Clark speaks during a presentation at the Negro Leagues Baseball Museum. Mandatory Credit: Denny Medley-USA TODAY Sports / © Denny Medley-USA TODAY Sports
