Initially, only five minutes of stoppage time was called for, but the referee let the match go two minutes past.
The loss snaps RSL's 11-game unbeaten streak. It is their first loss since May 11th, and just their second loss at home all season.
After the match, Kreis was extremely critical of referee Matthew Foerster.
"The level of consistency was as low as I’ve ever seen from any referee in MLS," Kreis said. "I don’t want to belabor the point about him being poor. He is going to be poor. It’s the 14th match of his entire career."
Real was once again playing without Kyle Beckerman, Nick Rimando, Tony Beltran and Alvaro Saborio, who are off with their respective Gold Cup teams. But Kreis didn't use that as an excuse tonight.
"This one the referee owns," Kreis said.
Robbie Findley put RSL ahead in the 56th minute with a header after Kansas City goalkeeper Jimmy Nielsen misplayed a ball in the box. The goal was Findley's 5th of the season.
But things really changed when Chris Wingert tugged on the jersey of Soony Saad, and was sent off in the 66th minute for a second yellow card.
Less than a minute after Wingert's ejection, KC capitalized on a ball sent into the middle that RSL failed to clear. After a scramble in the box, Claudio Bieler was able to head the ball forward to Saad, who whirled and hit the ball into the net from inside the goal box, leveling the match at one.
Rookie goalkeeper Jeff Attinella, making his first MLS start, played well enough to earn the draw, especially with RSL playing a man down for the final 35 minutes.
But in the 7th minute of stoppage time, after Real Salt Lake players pleaded with the referee that time was up, Opara rose up high on a great ball sent in to the box by Graham Zusi, giving Sporting the victory.
"It’s two teams that are winners," Kreis said. "Two teams that want to compete really badly and to win really, really badly, and I think we’re fighting for respect."
Real Salt Lake returns to action to face New York July 27th at 5:00 p.m. on ABC 4 Utah.