Northampton were made to sweat by a battling London Irish before the reigning Aviva Premiership champions extended their lead at the top of the table with a 15-9 win.
Tries from Ken Pisi and Sam Dickinson plus five points from the boot of Stephen Myler secured a scrappy victory on a greasy pitch for the Saints, who are now five points clear of second-placed Bath.
Shane Geraghty kicked all of Irish's points as the visitors had the home side clinging on at the end.
Northampton made a host of mistakes and blew plenty of chances to give Irish a sniff of a shock win with the home pack only just holding out a last minute line-out drive.
Northampton had already squandered one try-scoring opportunity when Tom Stephenson dropped the ball on the line after Geraghty had missed a bouncing ball.
That was decided by TMO Sean Davey and a minute later he was back in action when Pisi dived to ground a cross-field kick from Myler.
The replays showed Pisi had just touched down before the ball went dead. Myler converted from the touchline to give Saints a 7-0 lead after 28 minutes.
Without Alex Corbisiero, due to a calf injury, and Dylan Hartley on England duty, Saints did not have it all their own way in the scrum all game and another penalty against the home front-row, saw Geraghty slot a simple three points to make it 7-3.
Geraghty missed a second penalty on half-time. That came after the home crowd were incensed to see referee Andrew Small, with the help of the TMO, issue yellow cards to props Salesi Ma'afu and Irish's Tom Court.
Ma'afu was sent to the bin for holding onto Court's leg after the pair came out of an Irish maul that had already won a penalty, while the former Ireland loosehead was carded for retaliating with a stamp.
The home side should have extended their lead within five minutes of the restart when they worked a three-on-two off a line-out drive, but a poor pass from Fotuali'i saw Pisi drop the ball short of the line.
Within four minutes of both sides returning to 15 men, Irish number eight Tom Guest was yellow-carded for coming into the side of a Saints maul that was steaming to the try-line.
At the second attempt Northampton did drive over with Dickinson claiming the try. Myler missed the conversion, but Geraghty landed a long-range penalty to make it 12-6.
It was turning into a niggly affair with Saints skipper Phil Dowson losing his cool and giving away a penalty in an off-the-ball scuffle. Myler tried to calm things with a penalty, but Geraghty immediately replied with three points for Irish.
The visitors sensed a shock win and when they shoved Northampton off their own scrum, the Irish forwards were within inches of battering their way over until the ball was lost forward.
Then a series of penalties gave Irish a five-metre line-out drive but Saints manage to shove it into touch inches short.