Call-up Brian Johnson twirls shutout as Red Sox silence sinking Mariners

Credit: The Associated PressThe Red Sox starting pitching is so hot even their spot starters are tossing gems.

Triple-A call-up Brian Johnson threw a five-hit shutout in his third major league start and the Sox extended their winning streak to six games with a 6-0 win at Fenway Park on Saturday.

Sox pitching hasn’t allowed a run since Texas scored in the sixth inning on Thursday, a run of 21 scoreless frames. Meanwhile Sox starters have earned the win and pitched at least six innings in each of the games during their winning streak.

The 26-year-old Johnson (2-0), who had thrown 91⁄3 innings total and recorded an ERA of 7.71 in his first two big-league appearances, exploited a Mariners offense…