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.
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.
Machado had right knee surgery in August and Wieters underwent Tommy John surgery in June.
"With both of these guys, it will be when and not if. I think if you held a gun up to my head, I think Manny makes the start of the year, and I think Matt is very close thereafter, but we won’t put either one of these guys on the field until it’s time to go, and try to keep the finish line in mind," Showalter said.
"I can't expect Alex to be anything," Cashman said during a phone interview Tuesday with The Associated Press. "Even before the suspension, he wasn't the same player at third base on the defensive or offensive side.
"We look forward to him hopefully solidifying himself as a tremendous DH for us."
The New York Daily News published a report Monday citing a source saying Rodriguez is determined to regain his role as an everyday third baseman. However, New York re-signed Chase Headley to a four-year deal to be the team's starting third baseman.
"In his mind, he’s still the third baseman," the source said. “That was before (Headley was re-signed) today, anyway.
"Based on what he was being told by the Yankees, Alex believed he would get the chance to play third base, and he believes he can do it. He’s motivated by it because he loves to play the field."
The Yankees re-signed Chase Headley on Monday to be the team's primary third baseman.
"In his mind, he’s still the third baseman," the person said Monday. "That was before (Headley was re-signed) today, anyway.
"Based on what he was being told by the Yankees, Alex believed he would get the chance to play third base, and he believes he can do it. He’s motivated by it because he loves to play the field.
"Whatever (poor) decisions he’s made, he’s still addicted to the game and he says he’s working hard to be ready. He’s said to me, ‘people are going to be surprised,’ meaning he’s convinced he still has game."
Headley split the 2014 season between the Padres and Yankees, batting .243 with 13 home runs, 20 doubles and 49 RBI in 135 games. He hit .262 with six home runs, eight doubles and 17 RBI in 58 games with New York.
Headley has a career .265/.347/.409/.756 slash line in eight MLB seasons. He also has 93 home runs, 194 doubles and 418 RBI.
Yankees general manager Brian Cashman indicated during an interview Monday with NBC New York the team's desire to re-sign Headley, and apparently Headley's desire to stay in New York.
"I do know this -- Chase wants to be a Yankee," Cashman said, per NJ.com. "He was a tremendous acquisition in the second half. A great leader. A tremendous defender. A switch-hitter with great discipline. He kind of checks off every box that we’d like a prototypical Yankee to look like.
"If we can find common ground, I’d like to have him man third base as we move forward."
Castellanos committed 15 errors and had a .950 fielding percentage in 145 games at third base in 2014.
"His hands are solid and his arm is solid," Dombrowski said, per MLive.com. "He normally catches what he gets to, but we're looking to increase his quickness over there.
"There's no question, from a defensive perspective, that he needs to improve. But when I say that, we try to give him the benefit of the doubt. He hadn't played third base in a while."
Dombrowski also has confidence in Castellanos' offensive abilities after he hit just .259 with 11 home runs as a rookie.
"We think he has a chance to be a good offensive player," Dombrowski said. "He had a good solid year last year, and we think he's going to continue to get better. When you look at his numbers for a rookie, and in a pennant race, his offensive numbers were pretty good."
The Yankees are in search of a third baseman in case Rodriguez is unable to fill that void on an everyday basis. The 39-year-old hasn't played more than 140 games since 2007 and missed the 2014 campaign due to a season-long suspension for his involvement with the Biogenesis scandal.