Goals from Elias Kachunga and Paul Digby lifted Cambridge off the bottom of the table after a 2-0 win at Cambridge.
Both sides finished with 10 men, Crawley’s Rushian Hepburn-Murphy and the U’s James Gibbons receiving straight red cards within six minutes of each other in the second half.
Cambridge, winners of both of their games since Neil Harris has returned as head coach, are now six points from safety together with Crawley who have won only five of 24 league matches under Rob Elliot.
The Red Devils, with only one home win in 13 weeks, threatened inside the first 40 seconds when Kamari Doyle fired wide of keeper Nathan Bishop’s left-hand post.
Cambridge defender Kell Watts put a left foot shot just wide from the edge of the area before U’s striker Ryan Loft headed over when well placed at the far post from Josh Stokes’ cross.
Cambridge broke the deadlock after 33 minutes in front of 1300 travelling supporters when a corner by James Brophy was dropped by keeper Jojo Wollacott and a close-range shot by Kachunga went into the roof of the net off Doyle.
Crawley were reduced to 10 men for the last thirty minutes when Hepburn-Murphy was shown a straight red card by referee James Oldham for an off the ball clash with Kachunga.
And Cambridge took a firm grip on the game only four minutes when midfielder Digby headed in Brophy’s cross.
The U’s then went down to 10 men themselves when defender Gibbons saw red for a challenge on Charlie Barker.
Crawley were poor throughout and their first shot on target did not arrive until the 85th minute when a shot by Doyle was saved by keeper Bishop.
