The Red Bulls were the worst defensive team in last year’s MLS Cup playoffs, and that was before an offseason in which they fired their coach (an ex-center back), sold their top center back and had their other starting centerback retire.

In other words, if veteran newcomer Ronald Zubar isn’t really good, their defense could be FUBAR. Real bad.

“I think he’s going to be quite good,’’ said new coach Jesse Marsch, who was hired last month and doesn’t have much time to rebuild the heart of the Red Bulls’ defense after a season when their 50 goals allowed were tied for the most of any playoff team.

And this year’s team won’t have Thierry Henry’s offensive wizardry to overcome defensive mistakes. Henry retired after their playoff ouster, coach Mike Petke was fired, center back Jamison Olave was shipped to Real Salt Lake for allocation money, and Ibrahim Sekayga retired Monday to take a spot on Marsch’s staff.

Enter Zubar, a 29-year-old French center back who made his pro debut a dozen years ago, and has played for Marseille, Wolverhampton of the Premier League and most recently Ajaccio in France. The Red Bulls reached out to him last month, offering a chance to be the steadying force in an unstable back line, the mentor to inexperienced youngsters such as Andrew Jean-Baptiste, 22, and Matt Miazga, 19.

“He’s a beast. It’s almost like looking in the future, how I’ll probably be when I get older. He’s an animal back there,’’ said the Brooklyn-born Jean-Baptiste. “He and Damien [Perrinelle], both those guys have an incredible amount of experience.

“Regardless if I get playing time or not, I have two experienced guys in front of me that I can learn from, what they bring to the table. One played in the EPL that I wish to play in, and the other played in Ligue 1 in France that I also wish I could play in. Those are players I can learn from. In the next practice I might come with a notepad and a pen.’’

Which is exactly what Marsch had in mind.

“When I started to get to know Ronald, we had conversations,’’ Marsch said. “One of them was: ‘We’ve got a young center back named Matt Miazga who could benefit a lot from you. He’s a good player, he’s made some mistakes but he’s still maturing.’ Ronald’s comment to me was: ‘I can help with that, because I know what that’s like.’ He went through some of this in his own career.

“From the day he showed up, you could tell he’s a footballer. He thinks about the game. That’s the kind of guys I like. I do foresee Matt and Ronald having a very good relationship, and Andrew as well.’’

Miazga is a homegrown academy product whose comfort on the ball has led to some costly giveaways. The Red Bulls have Perrinelle on the roster and Jhon Kennedy Hurtado on trial, but they’re counting on Zubar as the anchor.

“They have a lot of ambition. I know here we want to achieve things,” Zubar said. “[Marsch] explained to me what he wants from me on and off the pitch. That was clear. I said to my wife after that: ‘We’re going to New York.’

“I’m close to 30, so I have experience playing in big clubs in Europe, in England. I’ve experienced everything, every kind of football and different positions. I’ve learned a lot from that.

“For me, if you want something, you always have to [work hard]. From that point, and [Marsch] knows what I’m like, he told me there are a lot of young players who need to learn. From 16, 17, when I was young, I was already captain of my team. That’s something I have already, I don’t need to force it, just talking and helping on the pitch. That’s what I’ll try to do here.

“I didn’t know [Miazga] before, but … [I’m] impressed because you see he’s comfortable on the ball, strong, quick – this guy has everything. As I told him … sometimes you can be too comfortable and that’s when you make a mistake. … Nothing is easy and I just said, ‘You are training as you play.’ Just make sure every day you are ready to train.’’