Portsmouth opened up an eight point gap over Sunderland with the 3-1 win at Fratton Park and Pompey boss Kenny Jackett has hailed his side's ruthlessness.
The League One clash was goalless at the break, with Sunderland well placed to make the 330-mile trip back to the North East with a point at least.
But within two minutes of the restart, the Black Cats found themselves a man and a goal down, Gareth Evans scoring the penalty following Glenn Loovens' foul on Oli Hawkins.
The veteran defender shown a straight red.
Ronan Curtis added a second before Luke O'Nien halved the deficit with a smart finish from close range. Ben Thompson's third in the 63rd minute wrapped up the win.
Sunderland have two games in hand over their promotion rivals but are now eight points adrift ahead of the visit of Bradford City on Boxing Day.
Jackett said: "Obviously I’m delighted with the win, particularly the second-half performance, but congratulations to the players for getting the 50 points before Christmas, it shows good consistency.
"I thought the first half was quite a cagey game and there was a big chance for Lynden Gooch just before half-time where MacGillivray has saved with his legs, which is a terrific save and a key save.
"Then obviously there was the sending off.
"After that [red card] I am pleased to say we didn’t show any nerves, we took the game to them and didn’t back off, which is pretty easy to slip into when you are ahead against 10-men.
"We deserved the three goals and could have had more.
"We did stay in control of the play, which is what you want against 10-men, it doesn’t always happen, particularly when you have a lead, but for us we really pushed on from that point and created a high number of chances.
"We took three of them, which got us the win, and capitalised on a man advantage, which is good to see and not as easy as you always think."
On Loovens' red, Jackett added: "I don’t think the referee had any other choice for the penalty and Gareth took it fantastically to give us the lead."