Lotte Giants pitcher Lee Seung-heon, who was struck in the head by a line drive May 17 and suffered a microfracture of his skull and slight internal bleeding, was released from the hospital Monday, a team spokesperson told ESPN.

Seung-heon, 21, didn't require surgery, is doing well and is expected to rejoin the team for rehab after a month of rest, the spokesperson said.

The liner struck the right side of the right-hander's head and he was taken away by ambulance.

Brock Dykxhoorn, briefly a teammate of Seung-heon's last year with the Giants, told ESPN that as far as he knows, none of the Giants pitchers or any others in the KBO wear protective inserts in their caps. "I did," said Dykxhoorn, now a free agent, "and although I didn't broadcast it to anyone, some took notice."

The hard-shelled cap insert Dykxhoorn uses is made by Safer Sports Technologies. SST founder and CEO Matt Meier told ESPN that after the Seung-heon injury, the Giants ordered three inserts and a company that supplies equipment to teams placed a larger order. Meier said they were the first orders he'd ever received from South Korea.

As ESPN has reported in recent years, a handful of major league pitchers -- including some who've been struck by liners to the head, such as Matt Shoemaker and Daniel Ponce De Leon -- use the SST carbon fiber head guards.

Meier said SST's newest model is handmade, lighter than its predecessors and reinforced with Kevlar.