Crewe manager Steve Davis has admitted that ill-discipline cost his team victory at Barnet on Saturday.
The Alex lost 2-0 at Underhill after defenders David Artell and Adam Dugdale had been sent off in the first half, the latter for a dangerous tackle.
"You can't go lunging in like that now," Davis told BBC Radio Stoke.
"What you do is give the referee the chance to send you off or book you. Those two have, quite honestly, cost us the game today."
He continued: "We had our moments and had we kept 11 men on the pitch, I'm sure we would have won the game quite convincingly."
Skipper Artell saw red in the 29th minute for a professional foul on Izale McLeod, with League Two's top goalscorer putting Barnet ahead from the resulting penalty.
Two minutes before half time, the Alex were reduced to nine men when Dugdale was punished for a reckless challenge on Ricky Holmes.
Michael Hector put the result beyond doubt with a second goal 13 minutes from time.
The last time Crewe had two players sent off in the same match was in September 2009, when Billy Jones and Patrick Ada were dismissed in a 3-2 home defeat by Bury, a game which proved to be Gudjon Thordarson's last in charge at Gresty Road.
Crewe have now received four red cards in the 12 matches since Davis took charge of first-team affairs.
Artell will be banned for the home game against Accrington on 4 February, while Dugdale will be suspended for the next three matches.
With his two first-choice central defenders missing, Davis said that he may look to add a player on loan before the transfer deadline on Tuesday.
"It leaves us short in that department," added the Crewe manager. "We'll have to look at it this week and maybe bring somebody in to cover that."