The Red Sox are in last place in the AL East and entered the day with a 39-51 record, placing them 10 1/2 games behind the first-place Orioles.
"It's an opportunity for us to invest in players who we feel are going to be here beyond 2014," said manager John Farrell. "While there may be other decisions that are forthcoming, we felt like the place we were going to start with was behind the plate. That brings Christian to us -- a guy that we are high on [for] his abilities, particularly as a defender, the ability to shut down the running game and someone who continues to develop as an offensive player."
Vazquez joined a roster that includes other key components to the future such as Xander Bogaerts, Jackie Bradley Jr., Mookie Betts and Rubby De La Rosa.
The 37-year-old Pierzynski struggled during his brief time in Boston after having a solid 2013 season for the Rangers.
"He was professional about it," said Farrell. "I can't say he was completely surprised, because when you get a call to come into the ballpark at 11 o'clock in the morning, you figure this isn't the normal daily schedule. He was appreciative, wished it had worked out better than it has. Mutually we wished one another all of the best."
The Red Sox hoped Pierzynski could be a good short-term replacement for departing free agent Jarrod Saltalamacchia and bridge the gap until Vazquez and Blake Swihart were ready to come to the Majors.
"The offense wasn't there," said general manager Ben Cherington. "I'm not trying to be critical of him. It wasn't any lack of effort on his part. It just wasn't there. When you sign A.J. Pierzynski, that's what you're hoping: You're hoping for left-hand offense at a premium position, and we thought that was important to the team. If we got that, it would complement the team.
"Obviously we had interest in a short-term deal because of some of the catchers coming. That left-hand offense just wasn't there consistently. And he knows that. Again, if our position or our team's performance is a little different, it may still not have happened right now. That was the one part that just didn't show up the way we hoped it would."
In 72 games with Boston, Pierzynski hit .254 with four homers and 31 RBIs. Pierzynski walked just nine times and had a .286 on-base percentage.
"As I explained to A.J., I take responsibility for where we are and if the team's record was different, we may not have done something like this right now," said Cherington. "But we are where we are, so we need to start looking at things a little bit differently and this is one part of that."
Pierzynski, a two-time All-Star and a Silver Slugger Award winner two years ago, has batted .282 with a .320 on-base percentage over the life of his big league career. He has played for the Twins, Giants, White Sox, Rangers and Red Sox in a career in which he has caught in 1,742 games.
"Yeah, you never want to see a teammate get released or have to leave for any reason," said Ross. "He's had a great Major League career up to this point. We wish him the best."