SAN FRANCISCO (AP) — Rookie Hector Sanchez spent the winter back home in Venezuela fine-tuning his swing while turning most of his attention to becoming a better defensive catcher. Day after day, he fueled his improvement with thoughts of making the Giants' opening day roster.

His power bat did a lot to earn him San Francisco's backup catcher job behind 2010 NL Rookie of the Year Buster Posey after an impressive spring, leaving Eli Whiteside as odd man out.

"It's a great opportunity for me," Sanchez said. "I was dreaming of this for a long time — to stay with the team and enjoy this moment. I want to help the team as much as I can."

Sanchez, the Rookie of the Year in his Venezuelan winter ball league after a great season with Tiburones de La Guaira, received word from manager Bruce Bochy on Wednesday morning that he made the team.

"He first told me 'congratulations and you did a good job,'" said Sanchez, who hit .339 with 40 RBIs in 51 winter ball games. "He was happy with how I played and that I'm working hard. I was content that I did what I needed to do."

San Francisco also traded catcher Chris Stewart to the New York Yankees for right-handed minor league reliever George Kontos. That move brings the roster to the 25-player limit for opening day Friday at defending division champion Arizona.

"The Yankees had been asking for a while and got a little more aggressive recently," Bochy said. "The way the team was shaping up we felt we could make this move."

The 22-year-old Sanchez is a switch-hitter with power who was batting .372 with four home runs and 10 RBIs this spring heading into the exhibition finale Wednesday against the Oakland Athletics, in which he was the designated hitter after the teams agreed to use a DH in the National League ballpark.

Sanchez worked tirelessly during winter ball in his native Venezuela to improve his defense, and Bochy said late Tuesday that he liked how the catcher handled the pitchers in a close game.

"We're taking a leap of faith," Bochy said. "You have to. We did with Buster. It's the only way you find out — you put him out there, you play him. ... He's earning it every day. ... He understands that's the priority, his defense. He's got a gift, he can hit."

Whiteside was optioned to Triple-A Fresno, along with right-hander Steve Edlefsen. Outfielder Gregor Blanco's contract was purchased from Fresno — and he also impressed this spring after spending the offseason as Sanchez's winter ball teammate.

Bochy called the demotion of Whiteside — San Francisco's backup catcher during the 2010 World Series championship run — among the hardest he has made.

"I will go and get some at-bats and try to get better," Whiteside said. "It's part of the game. It's not what I wanted to happen. Hector had a good spring and he had a good offseason in winter ball."

Brett Pill and Brandon Belt made the roster — with Pill playing Wednesday against a left-handed starter as Bochy says will often be the case this season. Bochy has hinted Belt could start at first base opening day with Aubrey Huff in left field.

Belt, who bounced between the majors and Triple-A last season, spent his winter ball experience focused on improving his consistency at the plate. He reached base safely with a hit or walk in his last nine spring games, batting .483 (14 for 29) with three walks. His 28 total hits were tied for second most in baseball entering play Wednesday.

"I feel good about how I performed this spring," said Belt, who cried a year ago when he made the team. "I had a goal in mind to come in and be consistent and have a good spring, and I feel I did that."

Also Wednesday, the Giants reassigned to Fresno infielder Joaquin Arias, outfielder Justin Christian and right-hander Jean Machi.