But the high profile full-back - who returned from the NFL to resume his rugby career - insists a much stronger defensive start can give home fans something to feed off against Italy this weekend.
Rees-Zammit believes the energy inside the Principality Stadium can be a decisive factor against an Italian team going for a historic three victories in the tournament, but only if the team give supporters something to rally behind from the outset.
The Bristol star has conceded the huge defeats to England and France made it difficult for fans to find their voice.
“It's hard for the crowd to get involved when we're not playing very well and we're letting in tries for fun early on in the game,” he said.
“I think when you have a good start to the game, that's when you can start bringing in your home fans, you can start playing better.
“The boys then feel the energy, and it just brings a bit of momentum to us. You've got to start well and bring the crowd into the game.”
Wales have shown signs of improvement since those opening losses, delivering far more competitive displays against Scotland and Ireland.
However, four tries were conceded in Dublin and Rees-Zammit believes the team must continue tightening up defensively if they are to build a foundation for success.
“Steve Tandy is a defence coach and I think you've got to sort out your defence first and then your attack will come,” he said.
“Because you don't want to be giving up 50 points and then having to try and score 51 points.”
According to the Bristol Bears back, progress has already been made since the early rounds of the tournament.
“You can see we're trying to build an identity and our defence has been a lot better since the first two games.
“We've really doubled down on that, but ultimately we got to double down on all the things we've done great over the last two games.”
Rees-Zammit has yet to add to his 16 international tries since his return, although he is also finding his feet at full-back, having been moved from wing.
The 25-year-old believes the squad are beginning to develop the understanding required to compete consistently at this level, particularly as players adapt to new systems and coaching methods.
“I think we've really started to do that the past two games,” he said. “That's why we've been able to put performances on that have been exciting for not just us playing, but people watching as well.”
Despite the narrow defeats to Scotland and Ireland - and the fact Wales have not won a game in the tournament for three years - Rees-Zammit remains convinced Wales are close to producing a complete performance.
“I think the past two games, I felt we should have won them both,” he said.
“But obviously they were two very good outfits in Scotland and Ireland, who have been together for a long, long time.”
“We're just building and I said it after the France game we've just got to start trusting each other.
“I think within the group, we brought real energy and then there were a lot of plays that turned the game around and went in our favour.
“An example of that - Alex Mann intercepting on our own try-line - that kind of thing just switches momentum.”
The former Gloucester player also pointed to the powerful connection between the team and their supporters when performances improve.
“It was amazing against Scotland, being at home,” he said.
“The fans give us so much energy, especially against Scotland that was an unbelievable feeling being on the pitch and hearing 70,000 people cheering for us.”
That atmosphere is something he hopes Wales can recreate against Italy — provided they avoid the slow starts that have hurt them earlier in the competition.
“I think it's going to be good this weekend being at home again for the final game,” he said.
“We will try and get the crowd into the game early on.
“I think in the first two games we let in tries in within the first three or four minutes of the game, so it's pretty hard for fans to get into the game after that.”
