Saracens director of rugby Mark McCall warned it is the business end of the Aviva Premiership that matters following the 22-12 victory over title rivals Harlequins at Twickenham Stoop.
The north London club opened up a four-point lead at the top of the table after dismantling Quins in the second half, Chris Ashton crossing in the 51st minute and Owen Farrell kicking five penalties and a conversion.
It was the first time in four matches that Saracens failed to finish with a try-scoring bonus point, but it was a result that confirmed them as the team to beat in the Premiership.
"In many ways that was the most satisfying win we've had this season," said McCall, who confirmed Farrell left the pitch late on with cramp only.
"Gloucester, Bath and Quins in a row was a tough ask, but it's been the manner of the way we started - we've played some decent rugby along the way.
"We've got off to a flyer, but Northampton look incredibly impressive. But it's not about how you start, it's about how you end.
"We just always want to be there or thereabouts and put ourselves in the frame for the top four, but we never look too far ahead."
Quins led 12-6 at half-time through four penalties from Nick Evans, but they were then picked apart with Saracens' power game forcing a succession of mistakes as they flung the ball wide out of hope.
"We were very good for most of the game. When you're down 12-6 teams can react by losing composure, but this group is very good at retaining composure and doing the right things," McCall said.
"We built pressure on them all the way through in that second half. We won the second half 16-0 and played really well."
"They're physically very powerful and were the better side on the day," O'Shea said.
"We played well in the first half, but in the second half we just didn't hold on to the ball for any length of time.
"Saracens have huge strength in depth and probably have most of their key players fit.
"Everyone knows they are an excellent team and will take some stopping, but Northampton went six from six at the start of last season. Things change drastically in the season.
"We're disappointed to lose at home, but it's important the players don't feel sorry for themselves.
"We're fine and I'm very comfortable with the group of players we have."