Walker (shoulder) is scheduled to throw a bullpen session Tuesday, Bill Ladson of MLB.com reports.
Walker played catch on the field in New York on Monday, and after throwing without any issue, he's been given the green light to toss a bullpen session. While it's good news that he's progressing through his throwing program, the Diamondbacks are unsure if he'll be ready to take the mound before the end of the 2019 campaign. Walker hasn't seen any big-league action since undergoing Tommy John surgery in April of 2018.