Rangers beat a coronavirus-depleted Celtic side 2-0 at Celtic Park on Saturday to move four points clear of their bitter rivals at the top of the Scottish Premiership.
Two goals from Connor Goldson proved enough for Steven Gerrard's men, who are desperate to stop their bitter rivals winning a record-breaking 10th consecutive title.
In the first Old Firm derby without fans, Goldson headed in James Tavernier's free-kick in the ninth minute and tapped in from close range in the second half as Rangers recorded back-to-back wins at Celtic Park for the first time since 1995.
It was a first domestic defeat since the last clash between the Glasgow giants in December for Neil Lennon's men, who have a game in hand over Rangers with a long title fight still to come.
Celtic were without star striker Odsonne Edouard, Nir Bitton and Hatem Elhamed due to Covid infections, while Ryan Christie missed out as he was forced to self-isolate for being a close contact of Southampton's Stuart Armstrong, who also tested positive, while on international duty with Scotland.
But Gerrard said that took nothing away from a dominant performance by his side.
"We've put in a really controlled, professional performance," Gerrard told Sky Sports. "I don't think we were at our fluent best but we've come here and controlled the game with and without the ball."
"We could maybe have scored more," he added. "There will be no getting carried away. We need to remain humble."
Rangers got the start they wanted when Goldson escaped his markers from Tavernier's searching free-kick and flashed a header past goalkeeper Vasilis Barkas.
Mohamed Elyounoussi wasted a good chance to level for Celtic but the hosts failed to manage a shot on target for the first time since 2009 in a league match.
Lennon pointed to his lack of options with James Forrest also out injured, while Albian Ajeti and Leigh Griffiths were not match fit.
"We had Ajeti not fully fit, Griffiths not fully fit, Edouard out," said Lennon. "That's three mainline strikers not able to start.
"But I felt we created good enough chances first half to score. Rangers defended their box pretty well today and that was the difference in terms of the psychology of the goals.
"We were pretty decimated with the Covid and the injuries but I felt we had a strong enough team out."
Earlier, the Scottish league said it would investigate after St Mirren's latest positive virus test led to the postponement of their clash with Motherwell.
Two players had already tested positive earlier this week, with a third forced into self-isolation.
A further positive test saw more players instructed to go into self-isolation and the club told the Scottish Professional Football League that they could not fulfil their Premiership fixture.