Union goalkeeper Zac MacMath has been upgraded from 'out' in Tuesday's injury report to 'probable' today, per a Tweet from the club.

MLS had not updated its injury report as of 6 p.m. MacMath has been suffering from concussion-like symptoms since a collision with Seattle's David Estrada in the first half of last weekend's loss to the Sounders. The second-year pro did not suit up for Wednesday's friendly vs. Schalke 04.

Times staff photo / JULIA WILKINSON

Though this seems like positive news, here's why MacMath should not play Sunday against visiting New York:

1. Concussions are far more severe than any other injury.
If MacMath Tuesday was suffering from symptoms related to a concussion, chances are it hasn't gone away in three days. And since MacMath has been the Union's best player this season -- by far -- the club will need him to be at the top of his game as the season progresses. An aggravated concussion leads to light and noise sensitivities, as well as headaches ... and that's only in the short term. The Union would be best served sitting MacMath.

2. Heightened sensitivities to concussions nationwide.
They are more than a buzzword or the hot topic of sports. Concussions are a serious epidemic, serious enough that the Union and PPL Park are promoting Sunday's match as Concussion Awareness Day. Taylor Twellman, an MLS all-star whose career was cut short by concussions, is an advocate for the awareness of the ailment. A former Union broadcaster, he'll be on hand with an ESPN team for the game. It would seem to undercut the message of the event should MacMath suit up.

So while Sunday is a big game against a big rival, it might be in everyone's best interests that MacMath take the day off and allow either of his backups -- Chase Harrison or Chris Konopka -- to get the start.