The Seattle Mariners will welcome back the ace of its starting rotation for a series-opener against the Boston Red Sox, while a right-handed reliever will be heading back to the Triple-A Tacoma Rainiers. The Mariners activated Logan Gilbert off the 15-day injured list and optioned Jackson Kowar to Tacoma in a corresponding move Monday. Gilbert will be making his first start since April 25 due to a right flexor strain.