Top 5 upsets of 2018 in men's tennis

#2 Thanasi Kokkinakis vs Roger Federer - Miami Masters Round of 64

Miami Open 2018 - Day 6

Roger Federer began the year in brilliant fashion, winning the Australian Open and the Rotterdam title to get to the world no.1 position. His 17-match win streak was snapped by Juan Martin del Potro in the Indian Wells Final just a few days before his first match of the Miami Masters.

He had to dig deep in Miami as well in order to keep his no. 1 ranking but to everyone's shock, he was upset by world no. 175 Thanasi Kokkinakis in the round of 64. He was not on top of his game and looked quite unfit as well but Kokkinakis played some great tennis to knock him out. He lost the world no.1 ranking in the process as well.

Result: Thanasi Kokkinakis def. Roger Federer 3-6, 6-3, 7-6

#1 John Millman vs Roger Federer - US Open Fourth Round

2018 US Open - Day 8

Federer had just come off an exceptional 3rd round encounter against Nick Kyrgios, which he won in straight sets. He was expected to produce a similar performance in the fourth round against John Millman as well, who was ranked outside the top 50.

He won the first set with relative ease and was up a break in the second set as well. However, what happened from there was quite unbelievable. He lost his serve and the set and then went on to lose the next two sets as well in tie-breaks, thus giving the match to Millman.

His game was riddled with unforced errors and his serve was extremely poor after the first set, with as many as 10 double-faults to his name. In the post-match press conference, he spoke about how the heat had affected him and how he wasn't able to breathe properly.

Result: John Millman def. Roger Federer 3-6, 7-5, 7-6(7), 7-6(3)