Brighton boss Gus Poyet admitted he was made to "suffer" before his side secured top spot in the Championship with a 2-1 win at Millwall.
The Seagulls were two up and apparently cruising to a fifth straight victory thanks to goals in each half from Ashley Barnes and Adam El-Abd.
And Millwall's hopes looked over when substitute Chris Taylor was red-carded midway through the second half.
But instead of seeing the game out, Brighton dropped deeper and the 10 men almost grabbed a shock point.
First former Albion loanee Chris Wood marked his full Lions debut with a goal 11 minutes from time and then, in injury time, the young striker had the chance to complete an unlikely comeback, only for Tomasz Kuszczak to pull off a stunning point-blank save.
"It's very nice to be top," said Poyet.
"But when you start in this league you know how difficult every game is, you need to be on the bench watching that last 20 minutes, with my team defending like mad, to know how much you have to suffer to get three points.
"Something happened for the first time to us. We were controlling the game at 11 v 11 and then when it was 11 v 10, we lost it.
"We are supposed to know how to play against 10 men and we didn't do it today.
"The last 20 minutes was unbelievable, the pressure they put us under. So it was a great three points."
Barnes slid in his second goal of the season after 17 minutes and Al-Abd swept home his first in nearly two years from a 50th-minute corner.
But the game turned when Taylor left a foot in when he went in for a 50-50 ball with Kuszczak, leaving the Brighton keeper in a heap and referee Andre Marriner waving a red card.
Millwall manager Kenny Jackett said: "My impression was it was a harsh decision.
"I asked the referee if he did catch him and he said he did, but Chris thought the ball was there to be won and any contact was none or minimal.
"He didn't go through the guy and it didn't warrant a sending-off."
While Brighton enjoy life at the top, at least until Monday when Blackpool face Huddersfield, Millwall slipped into the bottom three
"I was disappointed with the goals against us, we gave ourselves mountain to climb," added Jackett.
"Ultimately it was a mountain we nearly did climb with a lot of pressure and that late chance, but against a good side we can't be conceding that many goals.
"But I look at the table every day - and anyone who tells you they don't is lying."