Carlos Alcaraz's Shanghai Masters debut came to an end with a surprise last-16 defeat to Bulgaria's Grigor Dimitrov on Wednesday.

The world number one - who had to come from a break down twice against Dan Evans in the third round - took the first set against Dimitrov but ultimately succumbed to a 7-5 2-6 4-6 defeat in two hours and 10 minutes.

Alcaraz had won the previous three meetings between the pair, including at this year's Madrid Masters and Queen's Club Championships, both of which he went on to win.

However, the Wimbledon champion only took one of the five break points he brought up against Dimitrov and also hit two fewer winners than the 18th seed, who expressed his delight at being able to force Alcaraz into errors.

"I stayed in the match, that was the first thing, especially after the first set," Dimitrov said after the match. "I was serving very well throughout the first set and he made a few errors.

"I pushed him to make a lot of errors at certain moments. At 4-5 he played an amazing game and another at 6-5. I was creating a lot of opportunities.

"After the second break in the second set I think I understood his service games and was able to put more balls in and read his serve a bit better. I think in the third set it was a bit of cat-and-mouse. I think we both played a solid set. He made a few errors and I was very solid and served well when I had to."

A nervy start from Dimitrov saw the Bulgarian double-fault twice in his opening service game, but he fought off two break points to hold before drawing first blood in the fifth game.

Alcaraz broke back for 5-5 while Dimitrov was serving for the set, and an untimely unforced error from the 18th seed on serve saw the Spaniard establish a one-set lead, which was quickly wiped out.

The world number two kept his unforced error count low, but Dimitrov's near-impeccable serving and blistering forehand allowed the Bulgarian to force a decider, where Alcaraz lost serve in the third game and created no further openings on Dimitrov's serve.

Another unforced error brought up match point for Dimitrov, who worked Alcaraz across the court before completing the job with a forehand smash, setting up a quarter-final with Nicolas Jarry in the process thanks to the Chilean's win over Diego Schwartzman.

Elsewhere, Andrey Rublev and Ugo Humbert also progressed to the last eight courtesy of straight-sets wins over American duo Tommy Paul and J.J. Wolf respectively.