Ivo Karlovic approaches the practice desk at the Ecuador Open, writes his name with a blue pen on the sheet to book a court from 11.30-1.30, and specifies that he is looking for a practice partner.

He goes back to the hotel to sleep. Maybe when he returns to the Club Jacarandá, someone will have signed up to be his practice partner, so he can play some points. But when he gets back and checks the sheet, no one has written their name down next to his. In other columns he reads: Bellucci + Monteiro, Estrella + Zampieri, Cerratani + Oswald.

All the practice courts at 11.30 have at least two players booked in. All except for the court of the top seed in Quito. For the third time during his stay at the ATP World Tour 250 tournament - and for the thousandth time during his 17-year career - Karlovic must practise alone with his coach, the Serbian Petar Popovic.

He asks for three tubes of balls and walks towards practice court No. 7, while fans stare at him open-mouthed. Being 6'11" will cause that reaction. Once on the court, Ivo starts to warm up and Popovic gets on with his own routine, which he had when he competed on the ATP World Tour before retiring in 2008 at the age of 26.

"It's not that often that I get to practise with another player," explains Karlovic. "They don't really like to practise with me, but I don't have a problem with that. I have to see my coach almost every day on the other side of the net." Popovic laughs at his answer. They usually joke about this.

Almost no-one likes to hit with Karlovic because of his flat forehand, slice backhand and his lethal serve, which holds the record for more than 11,000 aces. While the majority of players look for consistency in points to build confidence, Karlovic tries to finish the points as quickly as possible. His style is uncomfortable. "They aren't used to my game and they can't find a rhythm.

"But I think this situation is an advantage," adds Karlovic, a winner of eight ATP World Tour titles and currently No. 18 in the Emirates ATP Rankings. "The less they practise with me, the less likely they are to get used to my game. I like having a unique playing style. The good thing about practising with Petar is that I can do specific work that I need to do."

Popovic, three years younger than Karlovic, isn't one of those coaches that leans against a wall to watch and observe a practice session. He sweats as much as or more than his player. "I understand the other players not practising with Ivo because there is zero rhythm playing against him. So it is up to me to be fit enough to practise with him. On holiday I practise three times a week and go to the gym." It's not for no reason. Every day, he waits to receive serves faster than 200 kilometres per hour.

The practice situation has strengthened the relationship between them. Karlovic doesn't know if one day someone is going to write their name next to his on the practice schedule, but the company of Popovic is a certainty. "Above everything, Petar is a friend. Then after that he is someone whom I've worked with the past three years. We spend a lot of time together and we get on very well. He is very funny."

"Our relationship is fun," explains Popovic. "Sometimes I tell him: 'Take this, do this.' And he says: 'Yes, dad!' It's funny because he is older and taller than me. We always find a way to laugh at ourselves. It's better to be like this because over the course of a year I see more of Ivo than my wife and children!"