Alexander Zverev celebrated his 21st birthday by edging a thrilling battle with French favourite Richard Gasquet to reach the Monte Carlo Masters semi-finals on Friday.

The German third seed came through a marathon final set under the lights just before 9pm to win 4-6, 6-2, 7-5 after two hours and 39 minutes.

Gasquet’s hopes of a first Masters semi-final appearance since 2013 were dashed in an incredible finish, and it will be Zverev who takes on Japan’s Kei Nishikori in the last four.

The world number four is looking for his third Masters title and hoping to bounce back from the disappointment of his final loss to John Isner in Miami.

Gasquet struggled to close out the first set and was broken when 5-2 in front, but did take it in the 10th game on his second set point with an exquisite drop shot.

The 31-year-old saw five break points come and go in the opening game of the second set, and Zverev took full advantage by moving 4-1 ahead.

The birthday boy wrapped up the set with ease to level the match, before breaking in the second game of the decider.

The pair then traded breaks of serve, both of which were sealed by rasping backhands up the line.

Gasquet provided a moment of brilliance to break again, finishing a sublime rally with a magnificent drop volley, only to fail to consolidate it in the following game.

The match looked destined to be decided in a tie-break, but Zverev broke French hearts with a fantastic backhand passing shot to grab his fourth win from four meetings with Gasquet.

Nishikori grinds down Cilic

Kei Nishikori, who returned from a four-month spell on the sidelines with a right wrist injury in January, battled past second seed Marin Cilic. He continued his excellent run in Monaco with a 6-4, 6-7 (1/7), 6-3 win.

Nishikori, who lost his only Grand Slam final to Cilic at the 2014 US Open, moves into a last-four clash with Alexander Zverev.

The Japanese was strong on serve from the outset, making a single break in a lengthy fifth game before securing the first set as Cilic found the net with a backhand.

Cilic saved five break points in the third game of the second set with some trademark big serving, following the hold with his first break of the Nishikori serve.

But he needed treatment on his right knee after the first point of the next game, and was broken straight back.

Nishikori continued to be the more consistent player, but he wasted three match points when serving for a semi-final place at 5-4.

And Cilic stormed through the tie-break as Nishikori lost his range.

The former world number four showed great resolve, though, and dug deep before breaking Cilic in the eighth game of the deciding set and clinching victory as the Croatian found the net.

With inputs from AFP