SCOTTSDALE, Ariz. -- Reserve catchers often toil in anonymity, but that's not so with the Giants.

The care and feeding of Buster Posey, who'll probably need periodic if not frequent breaks from catching to rest his repaired left leg, magnifies the importance of his backup. Though it's impossible to estimate how many games Posey will play behind the plate this season until the regular season tests his stamina, San Francisco's No. 2 catcher conceivably could start 50 games or more.

So while the health and playing status of second baseman Freddy Sanchez, closer Brian Wilson and Posey himself deservedly command attention, the competition for the second catching spot between Chris Stewart and Eli Whiteside shall remain a high-priority issue throughout the entire preseason schedule. Hector Sanchez, the rookie who's a dangerous switch-hitter, probably will begin the season at Triple-A Fresno to continue developing defensively.

Manager Bruce Bochy probably won't name a second catcher until after the April 4 exhibition finale against Oakland, reflecting why he recently said that the decision probably will be the most difficult one he faces this spring.

The similarities between Stewart and Whiteside abound. Both have spent the majority of their professional careers in the Minor Leagues. Neither hits impressively -- Stewart hit .204 last year and owns a .200 career batting average; Whiteside's corresponding numbers are .197 and .218. They described their partnership with the pitchers almost identically. Stewart: "It's the best staff in baseball. You can't ask for anything better as a catcher." Whiteside: "It's the best pitching staff in baseball, and being in my position, that's what you want to work with."

They also echoed each other regarding their pursuit of the same roster spot. They're more than aware that unless Bochy opts to open the season with three catchers -- an unlikely prospect -- one of them won't be a Giant after the first week of April.

"Even if I was the guy, I wouldn't want to come in with that attitude," Stewart said. "My attitude is, I have to win a job. It makes me better and at the end of the day, it makes the whole team better."

"You can't really worry about anything else," said Whiteside, who contributed a third-inning RBI single Tuesday as the Giants defeated the Los Angeles Dodgers, 8-4, in Glendale, Ariz. "I have to play as well as I can play and leave [the decision] up to them."

Statistically, Stewart outplayed Whiteside last season. Giants pitchers recorded a 2.70 ERA with him behind the plate, compared to Whiteside's respectable 3.30 figure. Stewart threw out 19 of 53 runners (35.8 percent) attempting to steal, eclipsing Whiteside's 13-for-66 success rate (19.7 percent). But Whiteside proved capable previously, particularly in 2009 when he caught five shutouts in 33 starts.

Whiteside's still recovering from a sore right elbow that hampered his throwing during a significant portion of last season.

"It's definitely not as strong as I want it to be or where I feel like it should be," Whiteside said. "It's still early. I feel I'm getting stronger, throwing every day and putting a little more on it every day, I can feel it catching up a little bit."

Whoever wins the backup job will have the pitching staff's confidence.

"They're both good game-callers and they have a lot of trust in what they're calling," left-hander Jeremy Affeldt said. "We were all very comfortable from the game-calling situation."

Said right-hander Ryan Vogelsong, including Posey in the mix, "I was perfectly fine with all three of them."

In this situation, three's probably a crowd.