Pacheco hit .255/.299/.333 in 153 at-bats between Colorado and Arizona in 2014. He made appearances at catcher, first base, second base and third base last season.
Ross hit just .184/.260/.368 in 152 at-bats with the Red Sox in 2014.
Pierzynski will fill a veteran presence to complement young catcher Christian Bethancourt, and the agreement also means the Braves are serious about moving forward with Evan Gattis in left field full-time, according to Eye On Baseball.
Pierzynski hit .251/.288/.337 in 338 at-bats between Boston and St. Louis in 2014. However, he managed to smack a combined 44 home runs over his previous two seasons.
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.
Ross, who was rumored to be headed to San Diego, has served as a backup throughout his career. His average has slipped in each of the last four seasons and dropped to .184 in 2014. It was his lowest mark in 10 years.
San Diego acquired Myers, catcher Ryan Hanigan, left-handed pitcher Jose Castillo and right-handed pitcher Gerardo Reyes from the Rays. Tampa Bay received catcher Rene Rivera, right-handed pitcher Burch Smith and infielder Jake Bauers from San Diego and outfielder Steven Souza and left-handed pitcher Travis Ott from Washington. Meanwhile, the Nationals received right-handed pitcher Joe Ross and a player to be named later, likely infielder Trea Turner, per CBSSports.com Baseball Insider Jon Heyman.
Ross addressed previous reports that he has signed a deal with San Diego on MLB Network Radio. "I do not have a deal with the Padres."
Ross will join fellow catcher Derek Norris and Tim Federowicz on the roster. He hit .184 over 152 at-bats last year with Boston.
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.
After dealing Yasmani Grandal to Los Angeles in the Matt Kemp deal, the Padres were in need of a new backstop. It didn't take long for them to replace Grandal, as the team acquired Norris shortly after the Kemp deal went through.
Pitcher Seth Streich will also head to the Padres in the deal, according to FoxSports.com The 23-year-old posted a 3.16 ERA over 114 innings in High A last season.
The 25-year-old Norris is coming off a season in which he hit .270/.361/.403 over 385 at-bats. Norris is under team control through the 2018 season.
Hahn, 25, posted a 3.07 ERA over 73 1/3 innings in the majors last year. He was excellent in Double-A, posting a 1.91 ERA in 42 1/3 innings before being called up.