Nelson will serve as the opener during Sunday's game against the Cardinals, Matt Gelb of The Athletic reports.
Nelson has pitched exclusively out of the bullpen to begin the season, but he'll make his first start of the year as Sunday's opener. He's lasted multiple innings in four of his last five appearances and has posted a 0.90 ERA and 0.70 WHIP in 10 innings during that time. Cristopher Sanchez will serve as the primary pitcher against St. Louis.