2018 Shanghai Masters Day 4: Juan Martin del Potro retires due to injury as Novak Djokovic and Roger Federer post contrasting wins

Day 4 of Rolex Shanghai Masters had a lot of promise and mostly the big names delivered with some incredible performances, but the ending wasn't quite what the crowd and fans all around the world would've hoped for.

It was another injury scare for Juan Martin del Potro during his 3rd round match against Borna Coric. At 5-4(30-40) in the first set, while returning a rally shot from Coric, del Potro slipped on the court in what looked like a rough fall. He sought medical attention one game later (was uncomfortable and ultimately got broken), and finally retired after he lost the first set 5-7.

This marks a 5th career Masters 1000 quarterfinal for Coric who sets up a quarterfinal against Matthew Ebden. Ebden won his 3rd round against Peter Gojowczyk 6-2 6-3 in just 50 minutes!

Although the end wasn't ideal, the morning session of the day's play was. 4th seeded Alexander Zverev came out all guns blazing and overpowered his Australian opponent, Alex de Minaur. Zverev blasted his way past De Minaur 6-1 6-4 in just 68 minutes to make his 10th Masters 1000 quarterfinal and become the youngest ever quarter-finalist in Shanghai. On Show Court 3, Kyle Edmund dispatched Nicolas Jarry 7-6(5) 6-3 to set up a tricky quarterfinal against Zverev.

On Center Court, much like Zverev, Novak Djokovic made little work of his opponent as well. In a rematch of their Roland Garros quarterfinal, Djokovic turned the tables against Marco Cecchinato and beat him 6-4 6-0 in 69 minutes to maintain his winning run.

Should he reach the semifinal, he'll be just 215 points shy of Rafael Nadal. But his road to semifinal won't be easy, as he faces an ever-improving Kevin Anderson who firmly dispatched Greek youngster Stefanos Tsitsipas 6-4 7-6(1), winning 82% first serve points and losing serve just once.

During the first night session match, Kei Nishikori delivered a brilliant performance against Sam Querrey to make the Shanghai Masters quarterfinals for the first time since 2011. The win gets him to #9 in the live race rankings, making him a contender to make it to London. Nishikori's performance is improving ever-so-steadily and he could very well pose as a serious threat against Swiss legend Roger Federer.

Federer's match against Roberto Bautista Agut of Spain was his easiest in the draw in terms of ranking. But a spirited performance from Agut made sure Federer had to toil much harder than expected to get the win. Despite a good serving day, he struggled against a hard-hitting Agut and for the second straight match, got stretched to 3 sets to get the win.

Federer ultimately survived the scare, much worse than his 2nd round match, to advance to the quarterfinals with a 6-3 2-6 6-4 score.

Friday's quarterfinals involve all potentially tricky match-ups. Zverev leads Edmund 3-0 in their H2H, but Edmund's recent form has been more convincing than Zverev. Anderson hasn't beaten Djokovic for over a decade but poses a challenge against Serbian with his current form. In the least-marquee match of the day, Borna Coric and Matthew Ebden face off for the first time ever. And, Friday's play caps off with a Federer vs Nishikori potential nail-biter.