Pearce, 35, was recently recalled from Triple-A Buffalo after completing a rehab assignment. When he has played in the majors this season, he has hit .291/.349/.519 with four home runs and 16 RBI in 86 plate appearances.
Espinal, 23, hit .314/.364/.478 with seven home runs and 32 RBI in 280 plate appearances at High-A Salem. He has mostly played second base but has also played third base and shortstop.
The Red Sox signed Brandon Phillips to a minor league deal on Wednesday, so the club is clearly stocking up on infield depth.