GUIDONIA MONTECELIO, Italy >> Outside the ropes, there’s another Europe vs. United States rivalry forming at the Ryder Cup.

These teams are singing songs, not making putts.

In the blue corner, it’s the “Guardians of the Cup” — a group of university pals from Nottingham in central England regaling the European players with playful ditties.

In the red corner, it’s the American Marshals, a group of friends from Minnesota wearing helmets with horns and going hoarse backing Zach Johnson’s U.S. team with their own easy-on-the-ear ballads.

They are both now fixtures at the biggest show in golf and are sure to be there early on Friday, taking their places on the front rows of the grandstands around the first tee.

And they have some new songs in their repertoire, including this by the Guardians for Europe’s newest star, Sweden’s Ludvig Åberg, to the tune of ABBA’s “Knowing Me, Knowing You.”

“Knowing me, knowing you … Åberg. There is nothing you can’t do.

“Knowing me, knowing you … Åberg. We cannot believe you turned pro in June.

“Playing golf is never easy, I know, but you’re now Team Blue.

“Knowing me, knowing you, Ludvig, we just love you.”

The Guardians are easy to spot in their yellow caps, sunglasses with yellow rims, blue waistcoats and trousers with dotted with golden stars on the front, and knee-high yellow socks.

They were golf-loving friends at the University of Nottingham and needed something to keep them tight after they left. They chose to meet up at Ryder Cups, starting with the 2010 matches at Celtic Manor.

“Back in those days, people weren’t dressing up at all and we thought we’d add a little bit of spice,” said Teddy Shuttleworth, a 44-year-old Guardian.

“We sat on the first tee — when you could actually get on the first tee without climbing through a hedge or sleeping under the grandstand — and Colin Montgomerie stood out at the front, takes his hat off to address the crowd and one of our guys shouts out, ‘You can keep your hat on!’ Suddenly that turns into a ‘You can keep your hat on’ routine.”

The group has become more organized, with Teams meetings and WhatsApp video calls to practice the songs. They are recognized by the European players — Justin Rose is known to be a fan, for example — and are regularly stopped for photos as they roam the course, as they were on a hot day at the Marco Simone club today.

“It’s great to see thousands and thousands of people coming together from across Europe to support the team,” said Cary Curtis, another member of the Guardians. “When does a continent come together like it does at the Ryder Cup?”

As for their U.S. equivalents, the American Marshals — a group of guys from Minneapolis — were originally labeled the “Minnesota Vikings” at their first Ryder Cup, also in 2010. There’s 13 of them because they like to see themselves as the 13th man of the U.S. team.

U.S. players Max Homa and Scottie Scheffler stopped putting on the practice green this afternoon to take photos of the Marshals as they serenaded the golfers with songs. Homa threw them a signed cap.

“We’re all friends living in Minnesota,” said Bill Rouse, 67. “We play golf together, we are family friends, everything. You’ll hear us on the first tee tomorrow. Loud and proud.”