SANTA CLARA >> After Miami Dolphins quarterback Tua Tagovailoa suffered what appeared to be his second concussion in five days Thursday night in Cincinnati, the NFL’s protocol for treating head injuries is once again under question around the league.

The 49ers who spoke about Tagovailoa’s injury expressed concern for the young quarterback and said that the players don’t have much choice but to trust the league’s protocols.

Tight end George Kittle, who has cleared sideline concussion tests in his career, put the onus on teams to save players from their innate desire to play through injuries, as serious as brain trauma is.

“It’s on the team to really protect these guys. Last night is a scary example of when a guy is not protected,” Kittle said Friday at his locker. “I’m not saying the Dolphins did anything wrong. Tua could have passed all these tests, and maybe his concussion last week wasn’t so bad; I don’t know all the details.

“With all the scrutiny that’s on it right now, I’m going to assume things are going to get even tighter moving forward,” Kittle added.

Cleared last Sunday by independent neurologists (per NFL rules) to return to a game against the Bills despite a hit that wobbled him, Tagovailoa took the field Thursday night in Cincinnati. He was sacked by the Bengals’ Josh Tupou in the first half, slamming his head against the turf with his hands displaying the “fencing response” that is often associated with a traumatic head injury.

“It was not a good look for our league,” 49ers general manager John Lynch said Friday morning on KNBR 680-AM.

Lynch endured multiple concussions as a hard-hitting safety en route to the Pro Football Hall of Fame, but the sight of a concussed player remains “a hard thing to take, kind of makes you queasy in your stomach.”

Jimmy Garoppolo called it a “scary situation” to see what happened to Tagovailoa. Of the multiple injuries Garoppolo’s endured the past four seasons (knee, ankle, calf, thumb shoulder), he hasn’t had a documented concussion.

DeMeco Ryans, the 49ers’ defensive coordinator and a former star linebacker, concurred that it was tough to watch Tagovailoa go down again Thursday night.

“We know he had one Sunday, and to have it happen again Thursday, it’s not something you want to see with anybody,” Ryans said. “Our game is nothing without players. And players’ health and safety is of the utmost importance. We’re hoping Tua is OK and we’re trusting those protocols are good.”

Former 49ers offensive lineman Randy Cross expressed his dismay via a Friday morning Tweet: “Tua was clearly concussed (the previous) Sunday and had zero business being allowed back in that game (against Buffalo). He also had zero business playing in a game 4 days later. The NFL should be embarrassed … if they can be.”

Arguably the 49ers’ most infamous concussions involved Hall of Fame quarterbacks Joe Montana and Steve Young. Montana was knocked from a 1986 divisional playoff after a concussion-causing hit from Jim Burt. Young’s final concussion came early in the 1999 season when sacked in Arizona, effectively ending his career.

Last December, the 49ers saw Trenton Cannon endure a concussion covering the opening kickoff, and after being taken by ambulance to a local hospital, he wasn’t cleared until the NFC Championship Game two months later. Nick Bosa exited the 49ers’ playoff opener at Dallas with a concussion but did not miss the ensuing win at Green Bay.

Of course, some concussions go unnoticed or undocumented publicly. Former 49ers tight end Greg Clark was 49 when he died by suicide last year, after privately battling what later was diagnosed as Stage 3 CTE — chronic traumatic encephalopathy — from a posthumous study by Boston University’s brain bank. “He totally was suffering in silence,” his widow, Carie Clark, recalled in April.

“Do I think they have our best interest in mind? The protocols since I was a rookie (in 2017), they’ve gotten way stricter and a lot better,” Kittle said. “... Sometimes the team has to protect you from yourself.”

Lynch lauded the NFL’s strides in concussion management. “From the days I played where it was, ‘Hey, how many fingers do I have up?’, and you’re back in the game, to (now), there is a thorough and laborious and so many cross-checks in the concussion protocol.”

Still, with so many independent evaluations necessary to keep playing, Lynch noted: “It begs the question, having what happened in Miami the week before: What went wrong there? Playing on a short week, he was cleared to play against Cincinnati last night.

“I can tell you, for real, that process is intense and has so many different avenues to catch a mistake,” Lynch added. “I can’t imagine it becoming more intense and more laborious, but I’m sure it will, and it’s important it is, because something was missed.”