From Joe Lowery at Backheeled. Last year 0.23 players were sent off per game in the regular MLS season. This year so far it is 0.35 per game, raising the frequency from once every 4-5 games to slightly more than 1 every 3 games. I'm even surprised the number was as high as 0.23 last year. I never thought it happened that often. This year, besides us, Charlotte, Dallas, Colorado and Montreal have faced shorthanded opponents at least twice. Yesterday Cincinnati won in extra time while shorthanded itself.
Aside from small sample size, Lowery has no theories to explain the increase and neither do I. But there have been a lot of red cards this year around the league.