This is Whalen's third stint with Seattle this season, though he's appeared in just one Major League game to date, taking the loss as a spot starter at Boston on May 27 when he gave up five earned runs in 5 1/3 innings.
With their rotation racked by injuries, the Mariners have attempted to alleviate the situation by rotating long relievers to prevent the rest of their bullpen from being worn down by too many short outings from the starters.
Curtis was recalled on Friday to replace Chase De Jong, who pitched four innings the previous day.