Juan Martin del Potro looked at the scoreboard after two sets, sensing that his US Open dream was coming to a close a weekend too early. Then, he must have remembered that his place in the pantheon of contemporary Tennis greats was once in the top four, above the likes of Andy Murray and Stanislas Wawrinka. Then, he strapped on his boots and conducted a comeback for the ages, assuring that he would play another day at the final Grand Slam event of the year.

Del Potro miraculous on Monday

The beginning of Monday's match couldn't have gone any worse for del Potro.

Dominic Thiem dominated him in the first set, taking it 6-1. The Latvian dominated the second set as well, 6-2. The Argentinian looked lethargic and frustrated with his own performance, as he should've been; it turns out, he was feeling under the weather, providing an explanation for how he started out. But a switch must have been flicked inside him, because he was ready to produce a US Open comeback unlike any in recent memory.

His serve and strong forehand started coming into focus in the third set, which del Potro won handily, 6-1. He ran into trouble once again in the fourth set. Thiem led 5-2 and even had a couple of match points when del Potro battled back, trailing 6-5, but a couple of aces put the Argentinian back in piloting position.

He then proceeded to finish the comeback in the fifth set, even though Thiem ended the match with more points -- two, to be exact. With that, del Potro moved on to the quarterfinals of this year's US Open.

The US Open draw going forward

Del Potro is no novice at the US Open -- he won the entire tournament back in 2009, before a wrist injury derailed his entire career.

But with many of the biggest names and faces dropping out of the tournament before it even began, he has a legitimate chance to revive his performance from eight years ago and win the whole thing.

His next test, however, will be his most challenging yet. He will be facing off against tournament darling Roger Federer in the quarterfinals on Wednesday.

They actually played back in the final that del Potro won in 2009, an epic match that lasted well over four hours. Del Potro will be exhausted after his most recent match, while Federer has already played some five-setters himself in the US Open, so neither can afford a drawn out match. The winner will play the victor between top-seeded Rafael Nadal and unseeded Andrey Rublev in the semifinals.