LI’s Mike DelGuidice went from living in a trailer to singing the National Anthem at the Ryder Cup, touring with Billy Joel

Now he’s the big shot.

An iconic Long Island musician who has been playing in Billy Joel’s band for more than a decade has the opportunity of a lifetime this Thursday by singing the National Anthem at the Ryder Cup, close to home at Bethpage Black.

“I’m petrified,” Mike DelGuidice of Miller Place told The Post just before seeing his massive stage at the Farmingdale golf course for the first time.

“I’ve done it at a lot of Rangers games, Knicks games, Mets, Yankees…but this one being what it is, it’s a little nerve-racking,” said the hometown hero, who has stolen the show countless times with his vocals and guitar skills during Joel’s longtime residency at Madison Square Garden.

Fretfulness aside, teeing up this career-defining moment is doubly exciting for DelGuidice as he has become a die-hard golfer over the past six years as well.

“I’ve probably played almost 30 courses on Long Island…When I do a gig at a country club, I always try to negotiate a free round,” said DelGuidice.

“My handicap dropped tremendously these past few years, but it’s a lot of work and it’s a frustrating game…and, I’m an avid watcher as much as a player.”

DelGuidice, who will sing during the opening ceremony, has a chance to meet some of his heroes on home turf at the state-owned Bethpage Black Golf Course in Nassau County, which has previously hosted the US Open in 2002 and again in 2009.

He will see the best American golfers, led by one-time close-by St. John’s University standout and Team USA captain Keegan Bradley, face Europe’s aces in three days of green grit for global pride from Friday through Sunday.

“I love Scottie Scheffler, but then again, I’m a huge fan of Bryson DeChambeau, I love Rory McIlroy. I don’t discriminate for any reason, whether it be country or anything,” he said of of the two Americans and the Northern Irish McIlroy.

“I don’t get starstruck easily when it comes to musicians or actors because I’m around that world a bit. But this is different because I watch these guys on a normal basis,” added DelGuidice, who loved their appearances in “Happy Gilmore 2.”

DelGuidice, a devout Mets fan, compared his opportunity to what it would be like singing in front of the crowd during the Amazins’ 1986 World Series championship.

And, while he has shot on some of the island’s most iconic courses like Sebonack Golf Club in Southampton, he has yet to try Bethpage Black, which features a bold-faced warning sign at the first tee box for its notorious, PGA-level difficulty.

“After this, I think I’m going to have to try my luck at it.”

Better on the back nine

It has also been a long time coming for the 54-year-old dad of four, who persevered through hard times at the start of his music journey.

“Right off the bat — just struggle, struggle, struggle. I was living in a motor home in my friend’s backyard. I just got divorced…so there was a lot of ‘when are you going to give up the dream? You’re never going to make it in music,’” DelGuidice said of his 20s.

“I just wouldn’t bend. I don’t know if it’s an Italian thing or a Long Island thing, or if it’s a genetic thing — You can’t tell me I can’t.”

The big break started to come while DelGuidice was two years into running an LI based Billy Joel cover band, which caught the attention of the famous Hicksville native himself in 2002.

They bonded over music, sharing the stage from time to time for the next decade, and in 2013, Joel asked DelGuidice a life-changing question during a rehearsal at the Paramount Theater in Huntington.

“He stood up and he’s walking away from the piano and he says, ‘I want to talk to Mike’…A couple of the people started gathering to hear what was going on, and he said, ‘No, I only want to talk to Mike alone.’”

Just like that, DelGuidice, now happily remarried, formally joined Joel’s ranks and was wavin’ the bad times goodbye.

“The beauty of that moment wasn’t even ‘oh wow, I’m getting to play with Billy Joel,’ it was an affirmation and a confirmation over everyone who said I couldn’t do this.”

Driving fore-ward

Nobody was more excited than Joel to learn that DelGuidice was selected to belt out the “Star Spangled Banner” as the Piano Man posted a “proud” photo of his colleague to Instagram earlier in the month.

DelGuidice said that he and Joel are of one mind in how the anthem should be properly performed.

“We’ve had many conversations about it. We’re both purists, so I approach the anthem in a very purist way,” said DelGuidice, who recently released a new single, “Killing Me,” and actively performs independently across LI and the nation as well.

He has opted to sing a cappella, although it is the most challenging rendition, which DelGuidice said is absolutely make or break on the very first note.

“There’s not going to be any finagling of the melody or, you know, doing any of the Whitney Houston stuff…it’s such a patriotic thing. You want to do it right, you want to do it justice,” he said, adding that the thousands in attendance are welcome to join in.

The time DelGuidice has spent on stage together with Joel has also inadvertently helped him prepare for this moment where the whole world will be watching.

During shows, DelGuidice would sing the operatic aria “Nessun Dorma” to lead into the hit “Scenes From an Italian Restaurant” — all because Joel loved a YouTube version he posted years ago.

Like with the upcoming anthem, DelGuidice had a pit in his stomach to jump from 80s rock to a track profoundly done by Luciano Pavarotti in front of thousands — but just as he plans to shortly, DelGuidice rose to the occasion.

“This is the moment — just try to stay in it and start on the right note,” he said, adding what an honor it is to represent the stars and stripes.

“Deliver it, just deliver it, and just get through it — and try not to drop dead of a heart attack midway through,” DelGuidice joked.