Golf fans quickly put their detective hats on to decipher what exactly was peering through Collin Morikawa’s trousers as he attempted to defend his Zozo Championship title.

It had been an eventful few days for the American, who earlier in the competition had fallen over when attempting a 151-yard recovery shot, but this time the viewers’ eyes were diverted to his wardrobe rather than his swing.

Eight Americans sit inside the top 12, behind leader Nicholas Echavarria, but Morikawa was not one of them. The two-time major champion carded E on moving day and finished tied for 39th, but continued to spark curiosity.

With his back to fans at the Accordia Golf Narashino Country Club, one supporter managed to snap a picture of Morikawa with an unlikely bulge pouring out of the back of his trousers.

Social media sleuths soon got to work on Reddit as they attempted to decipher the unidentified object.

And they quickly made light of the situation, as u/JMeucci was among many to say: “I thought everyone had a lucky butt plug, no?”

While u/Bogie2014 added: “Huge vibrating butt plug.” Then u/supisak1642 similarly joked: “Butt plug, all the good players are doing it, helps with concentration and those real intense butt hole pucker moments.”

However, despite the hilarious comments, in all likelihood Morikawa’s trousers were slightly askew and he simply had a spare golf ball or ball marker in his back pocket.

Some more reasonable social media users made the same point, as u/DrRickStudwell explained: “I get all the jokes but I’m actually genuinely curious what that could be. You can see the lining of the rear pockets so it’s not a golf ball that twisted the rear pockets during a swing or something.”

U/hoopaholik91 concurred, adding: “It's a golf ball or something else round in his right back pocket. Some of those pockets aren't sewn to the pant at the bottom so it can move around a bit.”

While u/m_ttl_ng similarly explained: “The lining of the right pocket is actually visibly curving toward the middle, if you zoom in on his a** and take a long hard look. I’m pretty sure those pants have a double back pocket with one having a zipper and the other being open. So I think it is actually a golf ball.”

Morikawa, however, has yet to publicly confirm the mystery as he instead sets his sights on finishing as strong as possible in one of his favourite events.

“The Zozo Championship is one of those tournaments that is highlighted on my schedule every year,” he wrote for Sky Sports earlier this week. “It's among a few, including Tiger Woods' event at the Genesis Invitational in Los Angeles that I really look forward to.

“Being half Japanese and having the opportunity to connect with the people in Japan over the years has meant a lot. Japan is one of my favourite countries in the entire world and I truly love being out there.”