SCOTTSDALE, Ariz. -- When Andrew Suarez kicked at the dirt on the bullpen mound Saturday and looked in at his catcher, most of what he saw was similar to every other bullpen session of his life. There was one key difference, though: An umpire in full uniform crouched behind the catcher.

Suarez fired a fastball, and the umpire emphatically pointed a finger to his left, signaling a strike.

"It was different, but I liked it," Suarez said. "You get a good feel for the plate."

The Giants have made a lot of subtle changes to drills under manager Gabe Kapler and a 13-person coaching staff. Pitchers fielded pop-ups Sunday, an extreme rarity in a sport where the default move for a pitcher is to get out of the way and let an infielder take over. The outfield drills more closely resemble the NFL combine, with cones meticulously set up and coaches focusing on change-of-direction. But the biggest difference through a week of camp has been the addition of three real professional umpires to bullpen sessions.

The Giants brought the umpires, who live locally, in for their second round of bullpen sessions. They have four mounds going at a time and pitchers could opt out if they preferred to just throw to a catcher, but they seemed to enjoy the extra touch of intensity. Kapler said it was something he did in Philadelphia.

"The concept obviously is to try to create heightened awareness and add a little competition to it," Kapler said.

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When Andrew Bailey met with coaches earlier this month, one thing the new pitching coach preached was making sure every pitch of every bullpen session had a purpose. The Giants record every session and pitchers can stop to watch video or get the spin rate or velocity on a previous pitch. The hope was that the addition of umpires would ramp up the intensity a bit, but Kapler said it wasn't just designed for pitchers.

"The catchers are getting some feedback," Kapler said. "The bullpen sessions are as much for the catchers as they are for the pitchers, and you see how much attention and emphasis our catching coaches are putting on receiving. I think it's been good so far."