''That was our primary goal going into this offseason; we wanted to address our starting pitching and ideally our catching,'' assistant general manager Thad Levine said.
The Rangers were already working on the Corporan deal when they got Gallardo in a trade with Milwaukee on Monday.
Houston designated Corporan for assignment Tuesday, setting up the trade for 19-year-old minor-league pitcher Akeem Bostick. The Rangers selected the right-hander in the second round of the 2013 amateur draft.
''We got to a point in the offseason where we knew we had to give up something to get a catcher, which is an important piece for the 2015 puzzle,'' Levine said. ''No different than the Gallardo deal, gave up a lot of quality players, but we filled some huge holes we had on our team, and much-needed players came back in our direction.''
Corporan, the Astros' backup catcher the past four seasons, is expected to have that same role in Texas behind Robinson Chirinos. Levine said the Rangers wanted a ''backup capable of handling more than a backup load.''
The right-hander was 89-64 with a 3.69 ERA in his eight seasons with Milwaukee, where his pitching coach during his rookie season in 2007 was Mike Maddux, now with the Rangers.
Gallardo took part in the team's winter camp Wednesday, throwing at the Rangers' ballpark where he has never pitched a game. He is eligible for free agency after this season, and has already made it clear that he would like to stay at home after that.
''This is a new chapter in my career, and I'm looking forward to getting started,'' Gallardo said. ''I think it's been 10 years since I stepped on the field. I had a tryout here actually before I got drafted, and here I am again.''
That actually would have been almost 11 years ago, before Gallardo was picked in the second round of the 2004 draft by Milwaukee out of Trimble Tech High School in Fort Worth, less than 20 miles from the ballpark.
NOTES: Darvish, who didn't pitch after Aug. 9 because of elbow inflammation, threw in the tarp-covered outfield Wednesday. Maddux said Darvish ''looked great, arm's working good.'' Darvish is on schedule to throw off a mound for the first time Feb. 2. ... 1B/DH/OF Mitch Moreland, the only remaining Texas player in arbitration, took part in workouts and said his surgically repaired left ankle is feeling good. He expects to be full speed at the start of spring training. Moreland has asked for $3,350,000, the team countered with $2,750,000. He made $2,650,000 last season when limited to 52 games. ... Right-hander Gonzalez Germen was designated for assignment by Texas to make room on the 40-man roster for Corporan. Texas got Germen from the New York Yankees for cash just a day earlier. The Yankees acquired him from the Mets last month.