Walker will serve as the opener during Monday's game against the Padres, Andrew Baggarly of The Athletic reports.

EDGE Analysis

Walker's first 11 major-league appearances have come as a reliever, and he's posted a 1.23 ERA and 1.02 WHIP in 14.2 innings. The right-hander hasn't tossed more than 51 pitches in any outing this year, but he'll begin Monday's series opener on the mound while Sean Manaea likely serves as a bulk reliever.