Minicozzi, 31, hit .298/.400/.470 with 12 home runs and 62 RBI in 315 at-bats with Triple-A San Jose in 2014. He has yet to appear in a regular-season game in the majors.
Hanigan, 34, is signed for two more seasons with a team option for 2017. He hit .218/.318/.324 with five home runs and 34 RBI in 225 at-bats in 2014.
Middlebrooks, 26, is eligible for arbitration for the first time after the 2015 season. He hit .191/.256/.265 with two home runs and 19 RBI in 215 at-bats in 2014.
Both pitched at a Class A level last season and averaged more than a strikeout per inning.
Prado is expected to assume the role of every-day third baseman for Miami. McGehee flashed virtually no power last season, but drove in 76 runs, batted .287 and committed just seven errors.
"Whether he's earned it or not, we don't know," Amaro told the Philadelphia Inquirer.
He has not earned it at the plate. Galvis owns a .218 lifetime batting average and hit a mere .176 with a meager .227 on-base percentage last season.
The deal will take care of one of the corner infield vacancies for the Padres. Middlebrooks has a career .237/.284/.411 slash line with 34 homers and 122 RBI over 830 at-bats through three seasons with the Red Sox. He has never played at Petco Field. Hanigan hit .218 with five home runs and 34 RBI over 225 at-bats last season with the Rays.
The 28-year-old Descalso has spent the last five seasons in the majors with the Cardinals. He has a .243/.313/.341/.654 slash line over 529 MLB games.
Callaspo signed during the winter meetings, but the team waited to make the deal official. Callaspo is set to make $3 million next season. He hit .223/.290/.290 over 404 at-bats last year.
"We're going to find out. It's going to be Pedro's job to keep," manager Clint Hurdle said, per the Pittsburgh Post-Gazette. "Pedro knows what challenges he's got to meet. He loves his teammates, he wants to do well and perform well. He's taken on some necessary opportunities this winter to prepare and get ready."