Although the Saints went on to record a club-record Aviva Premiership win over London Wasps, racking up an impressive 11 tries in a 74-13 victory, the opening quarter belonged to the visitors.
Charlie Davies followed up his own charge-down of a Lee Dickson clearance to open the scoring, before Tom Varndell was put away by Nathan Hughes, again from a charge-down, this time of a Ben Foden chip inside the Wasps half.
With Joe Carlisle adding a penalty Wasps had built up a 13-0 advantage and Franklin's Gardens was a nervy place.
But three tries in 13 minutes from George North, Phil Dowson and Stephen Myler settled the crowd, and when Luther Burrell scored before half-time the hosts had the point they needed to confirm that home semi-final.
After the break it was one-way traffic, with Lee Dickson scoring twice, North and Dowson both grabbing their second each and Tom Stephenson also dotting down.
Pisi himself rounded off a man of the match performance with a 69th-minute try, and while he was satisfied with the final score he was also realistic about the opening few minutes.
"It was good to win by that amount of points and we can take confidence and belief from the game," the Samoan international told SaintsTV. "Everyone was motivated; we wanted that home semi-final, and all the boys who started and came off the bench did their jobs well.
"But we know that against teams like Leicester and Saracens we can't afford to start like we did against Wasps. So we'll look at that and look to rectify what we did wrong."
The Saints Ticket Office is open between 10am and 2pm on Sunday, May 11th, for ticket sales for Friday's Aviva Premiership semi-final against Leicester. Ticket sales can also be made by Season Ticket Holders online; CLICK HERE for all the information.