Paul Heatley's goal after just three minutes proved enough to seal a vital win for Premiership leaders Crusaders against third-placed Cliftonville.
Heatley raced on to a superb long ball by Billy Joe Burns and got past keeper Conor Devlin to score the winner.
Burns was later sent-off for two yellow cards while Cliftonville substitute George McMullan got a red for comments made from the touchline.
Crusaders remain seven points ahead of second-placed Linfield.
Overall, referee Ross Dunlop issued two red cards and 11 yellow in what was a highly-competitive north Belfast derby.
Cliftonville, League Cup winners last weekend, now find themselves 12 adrift of the leaders.
They had a Johnny Flynn header ruled out for offside and also felt they should have been awarded a penalty for hand ball against Jordan Owens.
However, the points went to Crusaders and the way their players celebrated on the pitch after the final whistle, illustrated just how import the victory was as they go for back-to-back titles.
Cliftonville, champions in 2013 and 2014, really needed a victory to throw the title race wide open.
But now, many will view the battle for the Premiership crown as a two-horse race between the holders and David Healy's Linfield.
What they said
Crusaders scorer Paul Heatley: "In my opinion Cliftonville are out of it now, and I think most people will see it that way.
"We have been beaten just two times this season and it shows how consistent we have been.
"It is why we are 12 points ahead of Cliftonville of seven of Linfield with a game in hand."
Cliftonville manager Gerard Lyttle: "The big decisions didn't go our way today and we seemed to get all the bookings.
"It is not the first time we have come down here and the decisions have gone against us.
"Declan Caddell made about nine fouls before he actually got booked while we make one foul and get booked for it."