Rob Whalen's efforts to make the Mariners' Opening Day rotation were productive and encouraging, given his struggles in 2017. But he will not be a part of their immediate five-man unit, at least not for the time being.
Whalen, the Mariners' No. 21 prospect according to MLB Pipeline, was optioned to Triple-A Tacoma on Monday, one day after a rough outing in a 16-3 loss to the Indians. It was the lone blemish in an otherwise strong spring; he posted a 1.38 ERA over his first four outings, including a nine-strikeout gem against the Rockies last week.