Some might say Hunter Wendelstedt has umpiring in his blood. He learned the craft from his father, spent eight years in the minor leagues and has called numerous playoff games in his 13-year Major League Baseball career. ¶ But when Wendelstedt strides onto a diamond now, he knows he doesn't have the best eye in the ballpark anymore.

That eye, rather, is incased in a metal shell, hidden behind a glass lens, perched high above the center field fence, capturing 2.1 megapixels per frame. The camera sees all. It can zoom, freeze and slow down the action. Unlike a human, it never blinks. It never gets sick or tired, and once installed, it doesn't ask for more money.

"There's never a possibility for the human eye to be as good as these high-definition cameras. That just can't happen," Wendelstedt said. "With every advance in technology, not only does the game of baseball [change], but umpiring changes."

And the electronic eye is only getting more precise and pervasive. At the end of July, MLB Commissioner Bud Selig announced plans to expand video replay for the 2013 season, to include trapped balls and fair-vs.-foul decisions. The ease and exactitude of technology has enabled baseball to deliver more information and entertainment to its fans, while also establishing playcalling consistency and providing a "fifth eye" to determine boundary calls.

For umpires, the changes can be beneficial and positive. In the meantime, though, the innovations have altered aspects of how the game was traditionally called and played, which creates new challenges -- and, some say, a new rift between players and managers against umpires, who are suddenly under new levels of stress.

"It creates a lot of discussion on whether umpires are competent or not," former umpire Jim Evans said. "[Players] get called out on a strike and the first thing they want to do is run up the tunnel into the dressing room and look at the replay. It's definitely changed the game, and the role of the umpire."

Plate variables

Ask any of baseball's longtime managers or veteran players what the strike zone looked like a decade ago and the response might be a knowing chuckle.

"Every umpire is different," Twins manager Ron Gardenhire said. "Some of them like it high and some of them like the balls low, some of them won't give you this much off the plate but they'll give you this much inside."

Many like the variances, as long as the umpire stays consistent. But in 2001, concerned with the wide variation of strike zone interpretations, MLB implemented its first pitch-track system, QuesTec, to create a more consistent zone across the board, and to evaluate umpires in the process.

"Really, there should be uniformity to the strike zone," MLB spokesman Mike Teevan said. "Technology, in general, has helped us chart or define a strike zone that is the same for everybody."

The system was upgraded in 2009 to Zone Evaluation, a video tool installed at all 30 MLB ballparks that records a ball's position more than 20 times before it reaches home plate. That helped enforce the rulebook strike zone: a rectangular box that extends from the midpoint between a player's shoulders and the top of his pants down to the knees, over the 17-inch width of the plate. Previously, umpires were often calling a lower zone that went farther off the plate.

"All the sudden, they come in and say we want to get back to the rulebook strike zone, and I'm like, 'What do you mean get back to it?' Because it was never like that," said Evans, who said the size and shape of the original zone evolved through overall acceptance.

These days, younger pitchers are used to the textbook zone. But some veterans rue the shift.

"I think it takes the art of pitching away to a degree," said 39-year-old righthander Derek Lowe, recently signed by the Yankees. "Before, you used to be able to work guys off the plate a little bit more. Umpires would kind of work with you, and you could keep throwing them maybe a little bit further away as long as you could consistently hit that spot. ... The contact pitchers are going to struggle because the strike zone is so small."

Others see a different side, saying the "box" strike zone creates ump-to-ump consistency.

"It really just depends what side you're on," said Chicago White Sox catcher A.J. Pierzynski. "It's a no-win argument."

The problem, Wendelstedt says, comes with removing the individualities that made umpires special.

"Sure, they want umpires to conform, but we're all human beings and we're all different," he said.

Frayed nerves

Some players and managers say umps, with their authority questioned more, seem more on edge. This season, there have been several notable confrontations, from umpire Laz Diaz telling Yankees catcher Russell Martin he needed to "earn the privilege" of throwing the ball back to the pitcher, to umpire Bob Davidson yelling at Phillies skipper Charlie Manuel while he was still in the dugout. Wendelstedt and Gardenhire have gone at it plenty of times over the years.

"It's hard for you to talk to an umpire anymore, because you'll get thrown out of a game," Manuel said. "Nowadays ... they'll definitely retaliate. Or they'll bait you ... almost like they're embarrassing you in front of your team so you'll go argue with them." monitors ejections, and through Sunday, the site had tracked 131 this season involving managers, coaches and players. According to the site's data, there were 163 through the same date in 2011 and 144 in the same span in 2010. Generally, ejections have gone down in the past decade, according to MLB -- indicating many umpires have approached the changes with optimism and willingness. But if umps did feel extra stress, it would be understandable, players, coaches and managers say.

"I think I'd be on edge if everything was under a microscope and being looked over hundreds and hundreds of times," Phillies pitching coach Rich Dubee said.

At the same time, Wendelstedt points out, replay and pitch tracking end up proving the umpires are right a vast majority of the time. Most umpires score between 95 and 98 percent on the Zone Evaluation System, and each one of the 68 full-time MLB umps meet or exceed league standards for the machine.

"All we want, as umpires, is to get the call right," Wendelstedt said. "So if we can use a little bit of technology to make sure we get the calls correct, I'm in favor of it."

Umpires aren't in danger of being completely replaced by technology, Teevan said. Wendelstedt pointed out that umpires have other duties -- such as explaining rules, managing emotions and regulating things a machine couldn't detect, like the foreign substance found on Rays catcher Joel Peralta's glove earlier this year -- that make them invaluable.

Wendelstedt trusts his tried-and-true eyes, and he still relishes being on the field as much as ever. But he knows he has limitations.

"I think I have a set of high-definition eyes," he said. "But it's only one pair."