Nelson will break camp in the big-league bullpen, Matt Gelb of The Athletic reports.
Nelson, who was acquired from the Yankees in November, owns a 6.43 ERA in 35 career major-league innings, with his 16.1 percent walk rate standing out as a significant red flag. The Phillies will carry 10 relievers to start the season, but Nelson will have to pitch much better than he has in the past if he's to keep his job once rosters shrink back to 26 players in early May.