Soto is the only catcher on the Rangers' roster and was named the starter by general manager Jon Daniels and manager Ron Washington. Both said that Soto "is our guy" at catcher.
"We had a player that the more we talked about it, the more we liked what he brings to the table," Daniels said. "You don't want to ignore what's under your nose or put all your eggs in one basket from someone outside that you can't control. But we haven't ruled anything out."
"Anything" could be free agent Brian McCann, who hasn't ruled out the Rangers despite Soto's signing, according to his agent, BB Abbott.
Soto, who turns 31 in January, finished this season as the primary catcher for No. 1 pitcher Yu Darvish.
Soto was excited about the opportunity to be the Rangers' starting catcher.
"I mentally know these guys and what works for them in crunch time and what doesn't," Soto said. "You can know this guy has a slider or the other guy has a fastball, but when do you throw it? When does he have confidence in it? I think I have an ability to mentally get pitchers ready. I feel like I can make them give that extra bit."
Soto, who was acquired by the Rangers at the trade deadline in 2012, hit .245 in 54 games this season with nine home runs and 22 RBIs. He hit .324 after the All-Star break.
He was Darvish's regular catcher for most of the final month of the season, catching him every start after Darvish struggled in Oakland on Sept. 4, a game that included a disagreement between Darvish and starting catcher A.J. Pierzynski during a mound visit.
Soto was also Darvish's catcher as the ace of the Rangers' staff finished the 2012 season well after an up-and-down first four months in the big leagues.
Soto's .245 average was his highest since the 2010 season, when he also had 17 homers and hit .280 in 105 games with the Chicago Cubs.