They hoped it may be Danny Hobbs-Awoyemi or Nick Auterac.
But the player who has stepped up to take on the join as Waller's main competitor is in fact Manny Iyogun.
The talented youngster has actually done more than compete.
In fact, he has now become an important figure, often being given the nod in important games.
And with so much on the line this weekend and, from a Saints perspective, hopefully in the weeks after, Iyogun will again be trusted to help his club march on.
"It's been going pretty well and I'm enjoying my time here," Iyogun said.
"I've had some first-team game time and this is where I planned to be at the end of the season.
"I'm in a really good place and it's nice to be part of this.
"It's really enjoyable to still be in the race for a play-off place because a lot of teams have probably checked out at this stage and are thinking about going on holiday.
"We're very much focused and it's nice to be part of this environment.
"A lot of the boys have planned for a packed out stadium this weekend.
"It's going to be a really emotional experience with guys playing for the last time at the Gardens and we're going to channel that in our performance."
Iyogun has started seven games this season, including both of the last two, against Harlequins and Saracens.
And the 21-year-old said: "I'm learning bucketloads, constantly learning.
"Sue (Waller) is constantly teaching me stuff and people like Hilly (Paul Hill) are making me work hard in training so it's a constant learning experience.
"The biggest thing I've improved is how I looked after my body.
"This is my first season where I've been involved quite often in games and there's a physical toll it takes on my body.
"I have to be ready for the next game and it's been about body management.
“I’ve also had a different position in the squad this year with a much more inclusive role in the first team in terms of shadowing Sue and other looseheads.
"I’ve taken a bit more responsibility in terms of benching and starting and that’s reflected by my taking more of a leadership role around the scrum.
"It’s been good for my development and the coaches have been great in handing responsibility over to players.”
Iyogun speaks with plenty of maturity when he looks forward to a game that will decide whether Saints make the Gallagher Premiership play-offs.
They know a win against Newcastle Falcons at cinch Stadium at Franklin's Gardens would set up a semi-final at Leicester Tigers or Saracens on the following Saturday.
And Iyogun said: "We're definitely not looking past Newcastle.
"It's knockout rugby for us so if we lose this game the ball won't be in our court anymore and Gloucester could get in the top four with a win against Saracens.
"We're taking this next game seriously and we've had a great week training.”