Matt Hedges describes the feeling of playing with a cut right above his eye in Dallas' draw with NYCFC. (2:12)

Hedges not bothered by cut on his head - Via FC Dallas (2:12)

A pair of on-field incidents over the weekend brought the topic of MLS's evolving concussion protocol into focus for the league.

FC Dallas players Matt Hedges and Kellyn Acosta knocked heads during a match against New York City FC on Sunday, a collision so intense that Hedges required six stitches at half-time and had to change his jersey because of the blood.

Yet some viewers questioned whether either player was sufficiently checked for a concussion.

"I didn't know I was bleeding until everyone started saying it was," Hedges told reporters after the game. "They bandaged it up so I could go back in and then they stitched it up at halftime. ... I love to play and I don't really care if I am hurt or whatever, I just want to be out there."

Another scary incident occurred in the first half of Atlanta's game at Portland on Sunday. United's Yamil Asad was hit in the head by a ball kicked at close range and dropped limp to the turf. He returned to the game moments later.

Referee Alan Kelly said via a pool reporter that the "Atlanta medical staff determined after the check that he was fit to play. They sent him to the fourth official after the check."

But again, there were questions about whether Asad was properly evaluated.

Major League Soccer has an ever-evolving concussion protocol that has been developed by the league's 12-person Concussion Program Committee, which includes prominent neuropsychologist Dr. Ruben Echemendia.

The protocol is similar to the U.S. Soccer Federation's policy and guidelines adopted by other sports leagues. Players are evaluated using the Sport Concussion Assessment Tool, or SCAT, which is also used at the international level by FIFA. In addition to on-field assessment, concussion identification and return-to-play guidelines, the MLS protocol includes baseline testing.

New this season is the league's use of spotters who monitor each league match to help club medical personnel identify possible concussion cases.

Matt Hedges is helped off the field following a collision with teammate Kellyn Acosta left him needing stitches. USA Today Sports Images

"It's an area we're very focused on in ensuring that we're taking the best science possible and creating the best protocol we can from that science," MLS deputy commissioner Mark Abbott said.

Abbott said that in both cases last weekend, medical personnel made the on-field determination that the players could go back in the game. Also in both cases, additional evaluation was done later, either at half-time or after the match, and neither player was determined to be concussed.

In Asad's case, the physician for the Timbers raised the question about whether he should have been subject to additional on-field evaluation. The league is looking into whether further evaluation should have been conducted during the game, although Asad was cleared to play by further testing at the half, Abbott said.

It's up to the individual teams to follow the concussion protocol. That's something that former player-turned-ESPN broadcaster Taylor Twellman pointed to on Twitter this weekend.

He posted: "Until MLS holds their franchises accountable when they blatantly ignore the concussion protocol then serious progress can't be made."

Twellman is passionate about the issue. His MLS career was ultimately ended because of the lingering impact of a serious concussion. He founded the THINKTaylor foundation, which seeks to promote concussion education, safety and awareness.

Abbott said that if teams do not follow league policy, they are subject to discipline.

"If there is a violation of any league rule or policy, including this one which is very important, the people who are responsible to that violation are subject to sanctions, which could be fines or a variety of other things," he said.

MLS was part of a head injury and concussion summit just last month with U.S. Soccer and the National Women's Soccer League.