Maurer (1-4, 7.52 ERA) lasted at least five innings only twice in seven Major League starts after injuries to James Paxton, Taijuan Walker, Blake Beavan and Erasmo Ramirez's performance forced him into the starting rotation.
Manager Lloyd McClendon said Maurer underwent an MRI on Friday after complaining of back soreness following last night's start. But the fact the 23-year-old was demoted and not placed on the disabled list indicates he's healthy because a club isn't allowed to option an injured player to the Minor Leagues.
To help fill Maurer's roster spot, the Mariners recalled outfielder Endy Chavez from Triple-A Tacoma and put him in the leadoff spot while rookie James Jones was moved down to No. 2. In 37 games this season with the Rainiers, Chavez posted a .272/.289/.346 slash line with two doubles and no home runs. A 12-year MLB veteran, Chavez played for the Mariners in 2009 and 2013.
Meanwhile, Seattle placed Beavan on the 60-day disabled list. The right-hander had been on the 15-day disabled list since mid-April with tendinitis in his right shoulder.
Adam Lewis is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.