Powerhouse Argentinian Juan Martin del Potro has certainly ended his year on a high after closing out a Davis Cup victory for his country. The former No. 4's strong second half of 2016 has him all but pegged as a Grand Slam threat for 2017.

This year, he returned in Delray Beach, where he reached the semifinals. He hit his stride in Rio, earning a silver medal (but no ranking points) with wins over Novak Djokovic and Rafael Nadal.

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A quarterfinal showing at the US Open followed soon after, as did his 19th career title in Stockholm.

Don't forget Del Potro is also a former US Open champion. He pulled out a stunning victory over then-world No. 1 Roger Federer in the 2009 final, but battles with three wrist surgeries have kept the 28-year-old from really breaking through and reaching the peak of his game.

Late this season, his impressive come-from-behind defeat of Marin Cilic in the Davis Cup final as well as his five-set win over Andy Murray in the September semifinal may be just the momentum he needs to really hit his stride in 2017.

Peter Bodo's question for ESPN is what everyone is thinking: "Nadal and Federer are due to return this year, but who would feel confident in their prospects against the del Potro who has been raging in the second half of 2016?"

The coming year may be the right time for the 6'6" Argentine to slide back into the tennis elite. If anyone is able to give Stan Wawrinka, Djokovic, and Murray a run for their money, it's the unpredictable Del Potro.