A large majority of Red Sox fans here at Fenway Park stood for Marcelo Mayer ‘s first major league at-bat Saturday.

The Red Sox are calling up heralded infield prospect Marcelo Mayer from Triple A Worcester.

This season, however, Mayer has proven he’s more than ready for the majors. In 43 games for Triple-A Worcester, he hit .271 with an .818 OPS with nine homers, five doubles and a triple while providin...