Birighitti blames inexperience for the Jets finishing last season in eighth spot after conceding 45 goals– the equal third worst defensive record in the league.
Gary van Egmond has added 34-year-old former Netherlands international Kew Jaliens to his defence to try to make his side harder to break down.
Birighitti told the In Off The Post podcast that defence had been a key focus of the Jets' pre-season.
That focus appears to be working during pre-season, with the Jets keeping six clean sheets in nine friendlies, including in a 1-0 win over Sydney FC on Saturday.
"(Last season) we conceded so many soft goals in the first five minutes of games or just before half-time, just after half-time and I think it's just down to a lack of experience that we had in the centre of defence," Birighitti said.
"Average age of our back four I think was 22-23. You look at all the other defences like Central Coast Mariners with (Patrick) Zwaanswijk – he made a big difference.
"That's one thing we've definitely worked on in this pre-season is the back four and our defensive structure.
"Last year I remember we conceded something like 17 goals from set-pieces and that's just not on.
"We've been definitely working hard on it. Like I said, with Kew there, hopefully he can make a big difference and I'm sure he will."
Another of Newcastle's key signings in the off-season has been Nathan Burns, who has joined on loan from K-League club Incheon United.
Birighitti, 22, has backed his former Adelaide United team-mate to be a success at the Jets.
"I was lucky enough to play with Burnsy when I was in Adelaide and Burnsy is a fantastic player," Birighitti said.
"His technique and his pace to run at defenders and take a defender on is incredible. He will definitely work well with us."
Birighitti, who was given his Socceroos debut at the East Asian Cup in July, also backed Australia's head coach Holger Osieck.
The German is under increasing pressure after Australia were handed a 6-0 thrashing by Brazil in a friendly earlier this month.
"Whenever I had the chance to have a chat with Holger, it was all positive feedback from the tournament in general," Birighitti said.
"He's definitely a great coach, he's a strong character, he wants the best out of the players and he doesn't expect poor standards in training. Everything is at a high standard which is necessary at that level.
"I can understand all these stories coming about about overage players going to the World Cup. It's a fair point but he's the coach and at the end of the day, he picks the starting 11 and if he thinks that's the best starting 11 then so be it, you just have to deal with it."