Koschitzke was named on an extended bench with Trent Dennis-Lane, Arryn Siposs, Tom Hickey, Tom Lee, Farren Ray and Brodie Murdoch on Tuesday night.
The squad will be trimmed to 22 after the Saints train on Wednesday evening at Wellington's Westpac Stadium.
Watters said a final call on whether Koschitzke played would be made as late as Thursday morning.
"I think if you have a look at the squad that's named, he's listed as an emergency so if someone comes out of the 22, he'll go in," Watters said.
"At this stage he's an emergency, that's how we put it out.
"We have a couple of players we'll have a look at when we train this evening and then we'll make our final call the following morning, to be honest."
Sean Dempster has been named in the side but will have to prove on Wednesday that he is over the fractured hand he suffered in round two.
First-year player Josh Saunders has been named to start on the field while the other potential debutant Murdoch is listed on the extended bench.
Watters said the positive side of the Saints' injury list this year was the opportunity it had given to younger players.
"[Saunders] is a terrific kid, he's got great courage over the footy, good pace, good endurance, a developing player," he said.
"Another one in the mix is Brodie Murdoch, who we also see as being a strong player for us moving forward.
"I think we've used 33 players this year and we'll probably add to that tomorrow.
"Beau Maister breaks a thumb and you have those injuries at different times but it gives you fantastic opportunity to bring players in, so we see that as a real positive for us going forward."
Jennifer Phelan is a reporter for AFL Media. Follow her on Twitter @AFL_JenPhelan.
