Report: Red Sox tried trading for M's Castillo before Buehler signing

It looks like Walker Buehler was a backup plan for the Boston Red Sox.

Boston pivoted to signing the right-hander to a one-year deal after it was unsuccessful in trading for Seattle Mariners right-hander Luis Castillo, sources told MLB.com's Mark Feinsand.

The Mariners reportedly wanted first baseman Triston Casas in return for Castillo, but Boston was unwilling to part with the 24-year-old unless Seattle agreed to take Masataka Yoshida and the $55.8 million remaining on his contract.

The Red Sox signed Buehler to a one-year, $21.05-million contract after it became apparent a Castillo deal wouldn't happen, per Feinsand.

Boston had been linked to Castillo for weeks after reports claimed the Mariners wanted to move the 32-year-old and the $72 million remaining on his contract.

The Dominican, who posted a 3.64 ERA with 175 strikeouts in 175 1/3 innings last season, also apparently drew interest from the Baltimore Orioles, Chicago Cubs, and New York Mets.