Taylor Fritz crashed out of the Kinoshita Group Japan Open in Tokyo after a shock defeat in the Round of 16 to wildcard home player Shintaro Mochizuki, who won the tight battle 0-6, 6-4, 7-6 (2).

The World No. 10 was the defending champion at the ATP 500 tournament and had made a strong start to his campaign with a straight-sets win over World No. 18 Cameron Norrie in the first round. Meanwhile, Mochizuki is currently ranked No. 215 in the world and had just achieved his first-ever ATP Tour-level win with his opening-round victory against Toman Martin Etcheverry.

Therefore, it was no surprise when Fritz started the second-round clash dominant and in control. The American broke Mochizuki in his first service game as the latter racked up unforced errors and struggled on his second serve.

Fritz went on to get the double break as Mochizuki sought simply to get a game on the board, something which he was unable to do in the first set as his opponent secured the bagel and looked set to run away with the match.

However, things completely turned around in the second set, with Mochizuki pulling off an incredible comeback against the Top 10 player. They both held until 3-3, when the 20-year-old built up two break points, successfully converting the second to get ahead.

On the other hand, more unforced errors crept into Fritz's game, which saw him lose a lot of control over the match as Mochizuki succeeded in serving for the set to force a decider.

Both players came out fighting in the final set but it was Fritz who got an early lead, breaking Mochizuki in his third service game. At this point it looked as though the 25-year-old may have done enough to progress to the next round, but Mochizuki had other ideas.

As Fritz was serving for the match, his opponent hit two incredible backhand shots down the line before securing three break points with a drop shot. He then secured the first one to put the set back on serve.

Eventually, a tiebreak was required to decide the winner, with the Japanese player getting the mini-break on the first point. He then proceeded to keep his lead as Fritz searched desperately for answers.

Ultimately, though, it was too late as Mochizuki won the first of four match points in the tiebreak to book his spot in the quarter-final of the Japan Open, ousting the defending champion in what tennis journalist José Morgado called "one of the biggest upsets of the year."