Masahiro Tanaka told ESPN on Thursday that when he threw 20 pitches two days earlier during batting practice, he wore a hard-shell protective cap insert for the first time and plans to wear it in games this season.

The Yankees right-hander suffered a concussion July 4, minutes into the team's first summer workout, when a line drive that left Giancarlo Stanton's bat at an estimated 112 miles an hour struck the right side of his head.

The Yankees don't have Tanaka on their opening day roster but say he might pitch July 31. After the scary episode, he was taken to the hospital for tests, released the same day and placed under Major League Baseball's concussion protocol. Ten days later he told the media he had no lingering symptoms.

Tanaka said Thursday through an interpreter that he received the insert from the team's trainers Tuesday before that first throwing session since his injury.

"There really wasn't any discomfort when I initially tried it, so I decided to use it during live BP," said Tanaka. "It really didn't bother me there either, so I like these particular cap inserts."

Matt Meier, founder and CEO of manufacturer Safer Sports Technologies, told ESPN on Thursday that the current iteration of the company's "Pro Performance" carbon-fiber inserts -- provided to Tanaka and the Yankees -- are handmade, reinforced with Kevlar, have polyurethane-based padding, weigh about 1.2 ounces and measure about 7.5 inches in length, 4 inches in height and 0.195 inches in thickness.

Meier said SST sent the Yankees six of the contoured head guards, including the one for Tanaka, as the team requested enough for some other pitchers to try.

Big league pitchers can wear any protective headwear, even if MLB and the MLB Players Association haven't tested and approved the product, as long as MLB doesn't determine that it interferes with competition or licensing agreements. Meier said he has never submitted an SST insert for MLB/MLBPA safety testing, but is now leaning toward doing so.

In the past several years, MLB and the players' union have jointly approved two protective headwear devices after conducting testing, but pitchers never embraced either -- one a large foam, exterior-padded hat worn in games only by then-major leaguer Alex Torres in 2014 and '15 and the other an MLB/union-commissioned hybrid cap-helmet resembling a visor that some pitchers tried out in 2016 spring training workouts.

Another company's Kevlar safety insert that didn't have the imprimatur of MLB/MLBPA was worn by two MLB pitchers in 2015 games, but doesn't appear to have been used since then in the MLB regular season.

"I only knew about the large bulky ones," said Tanaka, adding, "I never thought of wearing that as I thought it would affect my performance on the mound."

Meier said his company's device is a partial insert, designed to protect one side of the head, because the impacts and injuries occur on the right side of the head for righties and the left side of the head for lefties, due to their follow-through position. A cap's appearance seems unchanged after the insert is secured with Velcro.

As ESPN has reported, MLB pitchers Daniel Ponce de Leon, Robbie Ray and Matt Shoemaker began wearing SST inserts after they were struck in the head by liners -- and in the cases of Ponce de Leon and Shoemaker, after having had injuries requiring brain surgery. Meier said he is aware of six other current MLB pitchers who wear it.

"We have major league pitchers wearing it who've been hit and others who haven't been hit and I would say 100 percent started in reaction to someone getting hit," said Meier, who lamented the reluctance of most to change anything about their routine.

"Not enough pitchers have tried it," said Meier of his company's head guard, "it doesn't create imbalance."

Meier said his sense is that the vast majority of pitchers think that if they haven't gotten hit in the head already, it won't happen to them and they don't need to protect against it. On average, about two MLB pitchers a year have been struck by liners to the head over the past decade.

"I'm sure pitchers have their preference for using head protection," said Tanaka, "but as I said earlier, there wasn't much discomfort for the one that I used, so I would probably recommend these ones to other pitchers who may be interested."