BIG serving German Jan-Lennard Struff has left the Monte Carlo Masters crowd shocked after producing an all-time comeback against Argentinian Sebastian Baez.

Heading in as the underdog against the South American who had already collected two clay court titles this season, Struff fought back from 6-1 5-2 down in the second set to win 10 of the next 13 games and claim a 1-6 7-6 6-2 victory.

Struff is coming off second round appearances at the Sunshine Double of Indian Wells and Miami, running into top 10 talents Jannik Sinner and Alex de Minaur at those respective events.

But while he has had a rough fixture this season, the German was able to overcome former top 20 talent Baez in an incredible performance.

Two players who could not be more different in the way they play, with Struff a powerful serving, hard-hitting European against a counter punching, reliable small South American – 23cm between them – it was the 33-year-old German who showed all of his experience in the pair’s first head-to-head.

Baez had the match all on his own terms in the first set, winning 71 and 50 per cent of his first and second serve points respectively, while surprisingly breaking Struff three times.

The German could not get his game going, only holding once and being unable to break his opponent, he won just 38 per cent of his service points.

That continued throughout the second set until the eighth game, where, with his back against the wall, Struff found his groove. He held serve to go to 3-5, broke his opponent for the second time – having done it early in the set, then held to level it at 5-5. Baez managed to hold on to force a tiebreaker, but the German’s momentum saw him win it, 7-3.

Struff flipped the script in the deciding set, winning all of his 11 first serve points, and winning five of 10 off his second serve, not giving Baez a look in on serve. By comparison, the Argentinian’s normally reliable serve failed as he no doubt rued the missed opportunity of the previous set.

Facing 11 break points, he saved nine of them, but the two breaks was still enough to see Struff claim the set 6-2, and the match in two hours and 23 minutes.

“It was a brutally close thing, I’m glad I won it,” Struff said post-match. “I’m very happy that I was able to turn it around somehow. I didn’t play well in the first two sets. Mentally “I wasn’t positive, but somehow I was able to improve the quality of my game again.”

Struff will now take on a red-hot Borna Coric who knocked off Kazakh 16th seed Alexander Bublik in a 6-1 6-1 demolition. The pair met in the opening round of Indian Wells a few weeks back with Struff getting home in a ridiculous 11-9 deciding tiebreak, winning 6-7 6-2 7-6.

In the other results, clay court talent Lorenzo Musetti proved too good for American 13th seed Taylor Fritz, defeating him 6-4 6-4, while Dutchman Tallon Griekspoor got past German Dominik Koepfer in a tight three-setter, 7-6 4-6 6-2.

Tonight’s schedule – that kicks off around 7pm AEST – features Aussie Alexei Popyrin taking on French qualifier Corentin Moutet, and Canadian Felix Auger-Aliassime facing another qualifier in Italian, Luca Nardi. In other matches throughout the night, Stefanos Tsitsipas meets Laslo Djere, Karen Khachanov goes head-to-head with Cameron Norrie, and Aussie qualifier Chris O’Connell meets Chilean claycourter Alejandro Tabilo.

MONTE CARLO ROUND OF 64 RESULTS:

Lorenzo Musetti (ITA) defeated [13] Taylor Fritz (USA) 6-4 6-4
Borna Coric (CRO) defeated [16] Alexander Bublik (KAZ) 6-1 6-1
Jan-Lennard Struff (GER) defeated Sebastian Baez (ARG) 1-6 7-6 6-2
Tallon Griekspoor (NED) defeated Dominik Koepfer (GER) 7-6 4-6 6-2