He's the son of a grizzled boxer and has a former world marathon champion on his team, so Alejandro Davidovich Fokina is no soft touch on a tennis court.
But get him talking about abandoned cats and dogs, then you are likely to see the Spaniard with the build of a middleweight put down his racquet and reach for a tissue.
"For me, they are not toys. When I see a video of animals abandoned, I almost cry," said the world number 46 who reached the last 16 of the French Open for the first time on Friday after a four-hour 35-minute toe-to-toe battle with in-form Casper Ruud.
In April this year, Davidovich Fokina launched Adoptas.org, a pet adoption platform which connects animal lovers wishing to take on a pet with shelters across Spain.
He said that Spain has a serious issue with abandoned cats and dogs.
"In Spain, we are the number one in Europe -- we have more than 300,000 abandons per year."
Davidovich Fokina, who celebrates his 22nd birthday on Saturday, called upon his own animal instincts to claim a 7-6 (7/3), 2-6, 7-6 (7/6), 0-6, 7-5 victory over Norwegian 15th seed Ruud.
He lived on his nerves in a 16-minute final service game in which he needed five match points to settle the affair.
Cheekily, he also saved a break point with an underarm serve.
It was a disappointing end for Ruud who had been tipped by many as a possible finalist having won the Geneva clay court title on the eve of Roland Garros and making the semi-finals in Monte Carlo, Madrid and Munich.
Former Wimbledon junior champion Davidovich Fokina reached the last 16 at the US Open in 2020 and he will face Federico Delbonis on Sunday for a first ever place in a Slam quarter-final.
Should he get through, he can thank his father Eduard for not being keen to see his son follow him into the ring, steering him towards tennis instead when he was just two.
Spanish marathon legend, Martin Fiz, the 1995 world champion, is also key, especially for the skills needed to conquer energy-sapping clay courts.
Fiz, who works on the player's mental approach, came on board after being asked by coach Jorge Aguirre.
"Alex is a 21-year-old player who is like a wild horse, pure energy and sometimes he wants things to happen too quickly," Aguirre told atptour.com.
"He needed help understanding that there is a process. Martin brings us his experiences from outside of tennis, which can be really useful to us if we use them correctly."
Friday's win was a first against a top 20 player.
But Davidovich Fokina has shown glimpses of clay court ability on the European swing, making the quarter-finals in Monte Carlo where he was stopped by world number five Stefanos Tsitsipas.
At the Rome Masters, he came through qualifying to make the third round where his run was ended by Novak Djokovic.
"You never really know what's gonna come out of his racquet," Ruud said of the Spaniard.
"He can produce extremely good shots and extreme winners, passing shots, beautiful drop shots. But sometimes he can also do more mistakes," said the Norwegian.