Before this Minnesota United season, Joe Greenspan had never had a concussion. In the past five months, the defender has endured three.

The latest, suffered in conjunction with a broken nose in Wednesday’s 0-0 draw against Houston after a collision with teammate Jerome Thiesson, will keep Greenspan out of the Loons’ lineup for Saturday afternoon’s nationally televised matchup against the New York Red Bulls at TCF Bank Stadium.

“It’s strange. I don’t know. It feels as though it’s a modern phenomenon. Maybe we didn’t know they were called concussions. We just thought we were dizzy and played,” coach Adrian Heath said, recalling his playing days back in the 1980s and ’90s. “But now, players get a bang on the head and then go to the doctor, and it’s a concussion. And I’m not saying it’s right or wrong, but it just seems more prevalent now than it’s ever been.”

United athletic trainer Sean Kupiec said in addition to the training staff watching from the sidelines for any potential injuries, MLS also has a spotting program, in which texts are sent to team physicians, via an iPad at the fourth official’s table, alerting them to concerns and showing videos of offending plays.

Concussions are risky business, Kupiec said, because they are nearly impossible to prevent — they can happen with or without contact — and deceptive. For Greenspan, his headaches could just as likely be from the broken nose as the concussion.

“Is it concerning? Absolutely, it’s concerning,” Kupiec said of Greenspan’s concussions. “But another thing that we’re looking for is how quickly do his symptoms resolve? … He is actually doing fantastic. His symptoms are very, very low right now, which is great.”

Greenspan, who was not available for an interview after Wednesday’s game, and several other key players will be on the sidelines as the Loons (5-11-4) continue their crucial four-match homestand Saturday against a Red Bulls club (9-8-2) looking to climb into the top four of the East standings.

Before each season (or when they first join a club), players undergo baseline concussion testing. Once a player has endured a concussion, he will sit with a neuropsychologist and test short- and long-term memory recall through such tasks as naming the months of the year in reverse or memorizing numbers and repeating them in a different order. There are several benchmarks he must meet in order to play again, starting with being symptom-free while at rest and eventually progressing to a full-contact practice.

Greenspan suffered his first concussion in training the first week of the season and recovered after about three weeks, in time to go on loan to Pittsburgh of the United Soccer League on April 10. His stint with the lower-division squad was successful, as Greenspan played every minute of eight matches, making the league’s Team of the Week twice and helping the Riverhounds to 3-3-2 with four clean sheets.

He returned from loan May 25 and made his first official appearance for United in June 14’s U.S. Open Cup match at Sporting Kansas City but left in the second half because of his second concussion after crashing into KC’s Roger Espinoza. It was another three-week recovery for Greenspan, who returned in time to be the Loons’ lone available center back in a 1-0 loss to the Columbus Crew on July 4.

Wednesday’s match, when he fell injured again, was just his second MLS start and match for United.

Greenspan’s misery, at least, has some company. Both backup goalkeeper Patrick McLain and starter Bobby Shuttleworth have endured concussions this season. Shuttleworth’s concussion, and a nice set of forehead stitches from the 2-2 draw at Houston on April 15, only kept him out of half of a match. Not even a month later, Shuttleworth broke his nose in a boot-to-face incident in United’s 2-0 win against Kansas City on May 7 but played through it.

“It’s pretty funny, we kind of went through the same exact thing, concussion and then a couple weeks later breaking the nose,” Shuttleworth said. “It can be very frustrating — almost as if everything is up against you. But I just said to him, ‘Stay positive, and you’ve got to keep moving forward.’ ”