Walker (blister) will not be able to make Sunday's planned start against the Marlins, Nick Piecoro of The Arizona Republic reports.
He said his blister is 90 percent healed, but it was preventing him from throwing his bullpen session on time, and thus he will be preemptively scratched from Sunday's targeted start. The Diamondbacks can take advantage of Monday's off day and work with a four-man rotation until June 10 against the Brewers, at which time Walker might be ready to step into the mix.