Santino Quaranta has had recurring headaches since he was elbowed in the temple, one of three United players affected by head injuries this season. (Richard A. Lipski/FOR THE WASHINGTON POST)

D.C. United’s Devon McTavish experienced whiplash in a preseason match. Teammate Kurt Morsink knocked heads with an opponent in the U.S. Open Cup. And United veteran Santino Quaranta was inadvertently elbowed in practice.

Different incidents, same outcome: a concussion.

As leagues at all levels — from youth sports to the professional ranks — take an increasingly serious approach to preventing and treating head injuries, United has felt the effect more than any other MLS club.

The severity varies. McTavish has yet to play this season and has pondered retirement. Morsink returned within two weeks. Quaranta has been sidelined for a few weeks and continues to experience headaches.

Their cases come in the wake of head injuries that forced D.C. defender Bryan Namoff and midfielder Josh Gros to retire in the prime of their careers, and led to the retirement of striker Alecko Eskandarian, who was initially injured while with United in 2005 and suffered additional setbacks with the Los Angeles Galaxy two years ago.

“It’s perplexing to me,” United Coach Ben Olsen said. “Are we spooked a little bit because we’ve had so many? I don’t know. It’s something the sports world is dealing with. The last thing I want to do is jeopardize someone’s life by putting them on the field when they shouldn’t be there.”

Inspired by Taylor Twellman, a onetime University of Maryland forward and MLS most valuable player who was forced to retire last year because of head injuries, the league has instituted new protocol to increase awareness and improve diagnosis and treatment. It hired neuropsychologist Ruben Echemendia, who worked with the NHL, to chair a 12-member concussion committee.

Players are administered preseason tests to establish a baseline in case of injury later on. Posters listing symptoms and recommendations hang in locker rooms and player lounges. The bottom of the banner features photos of five players driven from the sport by head injuries – three played for United.

“It’s definitely alarming,” United head athletic trainer Brian Goodstein said. “We’ve done the right things, and the symptoms haven’t gotten a lot better with some of these guys.”

While the NFL has turned to equipment improvements and rule changes to stem the concussion problem, MLS — and soccer in general — has realized there are no easy solutions. Most soccer concussions are the result of incidental contact, such as being struck by a fast-moving ball or being involved in a head-to-head collision.

Players are removed from activity quicker than in the past and MRI exams are administered.

McTavish, 26, was injured in a scrimmage against Florida International University in February. Knocked off balance, his head slammed into an opposing player’s chest and whipped back.

“I thought I’d be out two or three weeks, not where I am today. Every test comes back negative,” said the native of Winchester, Va., who has visited a neurologist; neuropsychologist; ear, nose and throat doctor; and optometrist. He will see concussion specialists in Pittsburgh on Monday. “I haven’t tried a witch doctor yet.”

He continues to experience headaches and pressure in his head, sometimes triggered by routine activity such as walking up stairs. His only previous diagnosed concussion was the result of a head-to-head collision in the 2009 season opener.

Quaranta, 26 and in his 11th MLS season, was elbowed in the temple during a workout. He left practice immediately and underwent testing.

“His memory recognition and cognitive skills were all fine, just headaches,” Goodstein said. “Unfortunately, that symptom hasn’t really gone away.”

Morsink was more fortunate. After a head-to-head incident — and subsequent treatment and rest — he was cleared to play within a couple of weeks.

Typically, a player must be symptom-free for three days before resuming gradual exercise, followed by monitoring under more vigorous work. If the symptoms return, it’s back to square one.

Pride and competitiveness also come into play.

“You start to think: ‘Am I being too soft about it? Should I just go back out there? Is it really that bad? But do I risk my future?’ ” Morsink said. “You just have to sit down.”

In his return to a competitive game, Morsink thought twice about heading the ball and chested it down instead. With the ball at his feet, he absorbed a tackle and injured his ankle, sidelining him for another extended period.

As for McTavish, a sixth-year pro, the future remains murky.

“I’m trying to get back and play,” he said. “You take it for granted, when you sit out for four months, how much you do love the game and how much you miss it. But you also have to think about your life.”

United note: Brazilian midfielder Fred, in his second stay with United, will move to Melbourne Heart in the Australian league next month, clearing valuable salary cap space, sources close to the situation said. Club officials declined comment.

Fred, 31, will remain on United’s active roster until the transfer window opens in mid-July. Before coming to MLS in 2007, he starred for Melbourne Victory. This year, he has appeared in 11 league matches, starting five and contributing one assist.