Sunderland have taken 31 points from 13 home games this season
Sunderland kept up the pressure at the top of the Championship with a narrow victory over 10-man Portsmouth.
The win keeps them in fourth, but only three points separate them from leaders Leeds United, with Burnley and Sheffield United in second and third.
Pompey suffered a fourth successive away defeat and remain just above the bottom three on goals scored from Hull City.
Wilson Isidor's eighth goal of the season after only seven minutes was the difference at the Stadium of Light where the Black Cats remain unbeaten.
The home side missed further chances to make the game safe against a Pompey side who played the final quarter with 10 men after captain Marlon Pack was sent off for bringing down Isidor when through on goal.
Sunderland's 3-1 win at Fratton Park in August made it four wins from four to begin life under Regis Le Bris and their form has been consistent since that flying start to keep them in touch with the leading pack.
The Black Cats wasted little time in taking the lead on a bitterly cold afternoon on Wearside.
They broke on Portsmouth from inside their own half with Eliezer Mayenda playing a ball through for the pacy Isidor to beat the offside trap and slip his finish past Nicolas Schmid who had come off his line.
It was Isidor's eighth goal in 23 matches since joining on loan from Zenit St Petersburg in August.
More chances came as Patrick Roberts' volley was kicked off the line by Ryley Towler after fine work from Adil Aouchiche, while a 25-yard strike from the Frenchman brought a strong save out of Schmid.
Isidor had the ball in the net for a second time, only for the goal to be ruled out for a correct marginal offside call.
Mayenda then spurned a golden opportunity on the stroke of half-time after he was put clear, the Spanish teenager lashing his shot into the side-netting.
The visitors had been second best in the opening half with Josh Murphy curling their best effort over after a purposeful run into the area.
John Mousinho's side have won only once on their travels this season - at QPR in October - and they are putting immense pressure on their form at Fratton Park to keep them up.
Colby Bishop had a good chance early in the second half, but the man who scored 21 times in League One last season headed wide after a bad kick from Sunderland goalkeeper Anthony Patterson gifted the visitors the ball in a promising position.
The home side resumed control and Isidor was close to a second as he bent one just past the post.
And when the French striker got the wrong side of Pack moments later, the Portsmouth skipper was shown a straight red for pulling him down.
New Pompey signing Rob Atkinson was sent on and the on-loan Bristol City defender made a goal-saving block to prevent Mayenda from making the game safe.
Without the cushion of a second goal, nerves grew and substitute Owen Moxon finally tested Patterson with an 89th-minute effort.
However, Sunderland closed out another win which means they have collected 31 points from their 13 home games, providing the basis for their unexpected promotion challenge.
Sunderland head coach Regis Le Bris told BBC Radio Newcastle:
"The early goal was important and opened the game for us. But Portsmouth did well with their own style of play and we struggled.
"It was better second half but we didn't score this second goal - 24 shots, many big chances, so the game was open until the end.
"Even if we didn't score this goal, we showed our consistency, which is good for a young team."
Portsmouth manager John Mousinho told BBC Radio Solent:
"I thought we played really well against a really good side with quality all over the pitch.
"I'm annoyed with the nature of the goal. We gave the ball away from a throw-in and we didn't deal with that quickly enough or well enough.
"But then we stayed in the game. We did that really well in the second half and we frustrated Sunderland for large parts.
"It was chalk and cheese from the last away performance - much, much better and a huge amount of improvement but some tiny bits to do to make sure we get there."
