The 2018 US Open starts Monday with Novak Djokovic as the favorite at +225 (bet $100 to win $225) at the Westgate Las Vegas SuperBook. Right behind Djokovic on the 2018 US Open odds board is Rafael Nadal, who who this tennis Grand Slam tournament last year over Kevin Anderson and is listed at +275. Five-time US Open champion Roger Federer is also a top 2018 US Open favorite, going off at +500. Nadal plays fellow Spaniard David Ferrer in the opening round, Djokovic will face Marton Fucsovics, and Federer squares off against Japan's Yoshihito Nishioka.

Before you make your 2018 US Open picks, you need to hear what renowned tennis bettor Sean Calvert has to say. At Wimbledon, Calvert predicted Kevin Anderson's stunning quarterfinal upset of Federer. Earlier this year, Calvert called John Isner winning the Miami Open at 100-1 -- a life-changing payout for those who followed his advice. In March, he nailed Juan Martin Del Porto winning Indian Wells at 10-1.

Calvert owns the US Open. In 2013, he nailed 25 of 28 US Open bets -- an insane 89.3 percent win rate that netted his followers nearly $2,700. The next year, his followers won $1,700. In 2015, Calvert called Flavia Pennetta's shocking women's title and it paid off at 499-1. Anyone who has followed him is way, way up. 

Now, Calvert has broken down the field and made his top US Open 2018 picks. In a stunner, he is fading Federer despite his 20 career Grand Slam victories, including the 2018 Australian Open. 

Calvert cites Federer's recent "sequence of losses," including his quarterfinal defeat to Anderson at Wimbledon and his second-round loss to Thanasi Kokkinakis at the Miami Open. Cavlert told SportsLine that Federer's "movement and return of serve" looked way off in Cincinnati. Adding to Federer's misery is his lackluster recent track record at the US Open. He has only made the final twice and hasn't won it all in a decade. There are much better values in the loaded 2018 US Open field.

Calvert is highly confident he has the 2018 US Open winner, and he's also backing a monumental long shot to go deep. Anyone who backs this underdog could reap a colossal payday.

Who wins the US Open? And what massive long shot stuns the tennis world? Visit SportsLine now to see Sean Calvert's picks, all from the acclaimed expert who cashed in huge on Federer's upset at Wimbledon and nailed John Isner winning the Miami Open at 100-1.