PITTSBURGH — Gunnar Henderson slides the leather onto his left hand. There’s no webbing, no pocket, none of the benefits of a modern baseball glove that make fielding easier.

It’s a flat glove — a round piece of leather more akin to an old-time mitt than the expertly crafted ones professional players wear on the field these days. But there’s a reason Henderson takes the field hours before first pitch with this flat mitt on his hand.

It’s difficult to field a grounder cleanly with one of these.

“So what do you have to do?” Orioles infield coach Tony Mansolino said. “You have to get yourself good hops. And where does that start? It starts with your recognition, your understanding and your perception of the hop and making the right reads. And then the next piece is the proper footwork to execute your read.”

That’s the next step for Henderson to master — to take his natural athleticism a step further by perfecting his footwork technique, which in turn will allow Henderson to field the routine play more smoothly.

And a flat glove is helping him do it.

“By putting a constraint on his glove,” Mansolino said, “it makes your feet work a little bit more.” And when Henderson’s footwork is better, “it makes catching the routine ground ball a little bit easier.”

At the beginning of spring training, Mansolino consulted a large Microsoft Word document he keeps on his computer that outlines the minor details he hopes to work on with infielders. In that document are also training techniques.

The flat mitt has been in baseball for many years, Mansolino said, but “it didn’t cross my mind” to use with Henderson until recently, having opted for other footwork techniques previously. The results have been strong, with Henderson implementing changes to his fielding technique almost immediately.

“His overall game has improved defensively, and Gunnar’s really, really athletic, and shortstop’s about being able to make the routine play,” manager Brandon Hyde said. “Just being a little bit more consistent with that, with his feet and his throwing.”

Henderson’s athleticism allows him to reach many balls at shortstop, and his arm stands out in the way he can turn would-be hits into outs. He showed both off Sunday, making a diving play in the sixth before nearly completing an unreal game-saving double play in the ninth had his rushed throw not missed the mark.

But, as Baltimore’s primary shortstop for the first time in his career, there are small areas for Henderson to refine.

Mansolino said last year the list of areas he wanted Henderson to improve was longer. It revolved around learning to throw from different arm angles, accurately throwing after a spin, and taking a deeper angle on a ball to his left before throwing.

This year, Henderson and Mansolino have narrowed their infield focus to improving double play feeds to second and Henderson’s footwork when fielding grounders. The flat mitt forces Henderson to bring his feet closer to the ball.

In doing so, he scraps two potential pitfalls.

With his feet closer to his hands, Henderson avoids the tendency to reach out his glove to the baseball rather than having softer hands, scooping the grounder into his body.

“That’s the biggest thing for me, just getting my feet moving, getting them ready for the game, and then my hands,” Henderson said. “And I feel like everything else is going to take care of itself. That’s just from reps of ground balls, and that just cleans up the fundamentals of things.”

And it eliminates a bad habit Henderson says he developed. Occasionally, Henderson would tap his right hand into his mitt before the ball arrived. Then he would reach down with his mitt alone. “That was kind of throwing off my timing,” Henderson said.

To field a grounder with his flat mitt, Henderson needs his right hand to assist his glove hand. Having two hands there allows a quicker transfer to throw and protects against a bobble.

“If it’s a routine ball, then you can get away with it,” Henderson said. “But it’s the ones that kick up right at the last second. If you stick it down and it comes up, you’re obviously going to miss it.”

Henderson is entrusted with the everyday shortstop role now. With that come heightened expectations for his defensive fortitude. The 22-year-old is up the challenge, and a flat glove is helping him meet it.