Salvador Perez is to the 2013 Royals as procreation is to mankind—necessary for survival. It gets mentioned here and there, but I don't know that it's been emphasized enough just how important Perez is to the Royals. He is among the three most important players on the team and arguably the most important.* When a team has a catcher who plays Hall-of-Fame caliber defense and puts up All-Star caliber offensive numbers, that guy is extremely important, essential actually.

*The other two are James Shields and Alex Gordon because I don't think many think the Royals have a chance to win without either of these three. Someone in the comments will inevitably mention Billy Butler, and while he's very important, he doesn't play defense and is a liability on the bases—barely missed the top three.

For proof, let's look at who replaced him during his time out of the lineup in 2012. While the Royals' record wasn't tremendously improved by his return, which was probably the result of his impact being offset by a slide from Mike Moustakas and the continued ineptness from the starting staff, his added value compared to those he replaced was ENORMOUS. In 74 games, Perez produced 2.6 WAR (from Fangraphs). Humberto Quintero racked up .3 in 43 games, Brayan Pena was -.3 in 68 games. In just a few more games than Pena, Perez was worth nearly 3 WAR more. That's incredible. His 2.6 WAR was ninth best in MLB among catchers, and he only had 305 PA.

From a strictly offensive standpoint, Perez simply produces more runs than most catchers in the league (and he'll turn 23 in May). Among qualifying catchers, Perez would have been eighth in wRC+ (weighted runs per PA plus) at 114, just behind A.J. Pierzynski—but he didn't qualify. Many of the other catchers on that list are primarily offensive catchers, guys like Pierzynski, Joe Mauer, and Ryan Doumit, and he hung with them in his age 22 season.

Back to Perez's stand-ins. Perez has a wRC of 41, which means by this measure he created 41 runs. In 340 combined PA, Quintero and Pena created only 25 runs, 10 for Quintero and 15 for Pena. Both of those were below league average per plate appearance. I'm not certain, but I don't see Brett Hayes doing much better.