The Wayne Bennett-coached side have completed at below 80 per cent in three of their four games so far, culminating in a sloppy effort in last week's 36-6 quarter-final victory over Papua New Guinea, where they completed just over half of their 46 sets.
In contrast, Tonga's ball control has been a feature of their campaign, averaging a 79 per cent rate so far and leaving Bennett clear on where his side must make progress.
"There's always room for improvement. We have just got to get our handling better, that's our major concern," Bennett said.
"We are much improved, there is no doubt about that.
"[But] the ball control is not exactly where I'd like it. There's been glimpses of it, been halves of it, we have just got to do it for a full game. But all the other areas are much improved."
Maintaining parity in the possession stakes also shapes as a key to getting over the top of Tonga and limiting the impact of their star-studded forward pack, led by Jason Taumalolo and Andrew Fifita.
Prop James Graham echoed his coach's calls, but took heart from the 36 points his side were able to generate from limited uses of the ball against the Kumuls.
"I think probably our ball control could be better, and that's just the standards that we set," Graham said.
"You look back to the weekend's game and we still managed to score 36 points off I think 26 completed sets, so I'd rather look at the positive side.
"But we are under no illusions that we are going to have to control the ball a little bit better if we are to get through this weekend.
"I think for us it's about playing well for 80 or potentially 90 minutes and staying in the moment. I have said this many times, that I think games like this take 80 or 90 minutes to win but only a moment to lose.
"So it's about staying focused the entire time you are on the field. Every moment, every tackle, we are going to have to be up for."