Rangers manager Steven Gerrard hailed his side's 1-0 win over 10-man Celtic as a "statement" victory as they opened up a 19-point lead at the top of the Scottish Premiership.
Celtic have three games in hand to try and close that gap, but a rampant Rangers look set to end the Hoops' run of nine straight titles after claiming a 14th consecutive league win.
The game turned on a red card for Celtic defender Nir Bitton after he hauled down Alfredo Morelos just after the hour mark.
Neil Lennon's men had dominated the first-half but could not find a way past Allan McGregor in the Rangers goal as he produced an outstanding save to turn Leigh Griffiths's shot onto the post.
And at the other end, Celtic's inability to defend set pieces, which has cost them all season, was exposed when the ball looped off Callum McGregor's shoulder into his own net.
"Today was big in terms of making a statement," said Gerrard, who has now guided the blue side of Glasgow to three consecutive derby wins.
"You're not always going to be pretty on the eye but it's about the outcome. It's certainly a positive sign, not being at our best, and getting the three points given where we are at this stage of the season."
Defeat piles more pressure on Lennon with Celtic already eliminated from European competition and the League Cup in a poor season so far.
The Scottish champions had come into the game on the back of six straight wins, though, and were the better side until Bitton's rash challenge undid the visitors.
However, Lennon claimed Morelos was not in a goalscoring position when he was pulled down by the Israeli international.
"I thought we were outstanding before the red card," said Lennon. "That changed the course of a game because we were dominating the play.
"We've been done by a pretty poor refereeing decision, I don't think he was great all day."
Rangers then held out for an 18th clean sheet in 22 league games this season to take a firm grip on the title race.
The Gers have not celebrated a major trophy since the club fell into liquidation in 2012 and tumbled down the leagues as a result.
Celtic have taken full advantage in that time, winning the last 12 domestic trophies on offer.
However, the tide has turned in Glasgow as former Liverpool captain Gerrard has slowly moulded Rangers into a force to contend with and now in his third season looks set to deliver the first silverware of his managerial career.