It is matches like tonight's at the Heineken Open that keeps the 34-year-old German Tommy Haas on the circuit.

Haas has earned $13 million over his playing career, so there are no financial reasons for him to keep flogging himself on tennis courts around the world, but it is match-ups like the one against French entertainer Gael Monfils in tonight's quarterfinal that keeps him going.

"These are the moments, while I'm still doing it," Haas said last night.

"It's why I am watching at certain times what I eat, training hard in the gym and being away from my family.

"I do this to test myself, to get into a big stadium in the Australian Open or play on centre court.

"When you're seven you dream of being a tennis professional player and when you've made it you're thankful and you're living your dream.

"It's not a real job, playing tennis. One day it will be over and real life will hit you. You might as well just enjoy it and have those ups and downs that come with it."

Haas beat dutchman Igor Sijsling in the second round yesterday while Monfils accounted for Australian Greg Jones.

Their match-up tonight should be a real thriller and is worthy of being a final. They have played each other twice before and shared the wins.

"He is a great player, a former top-10 player," Haas said of Monfils.

"He had a rough year last year with injuries and had some time away from the game, so I can feel how he's coming back now.

"He is eager to prove himself and get back into the top 10, but with every match he plays he is probably happy to be back out there and enjoying it.

"For me it's the same, I am happy playing at this level. We are both going to go out there and try to find our games, and it usually comes down to who's going to be better under the pressure, who plays the bigger points better.

"I know he moves well and can keep the ball in play quite some time, but also, he has a lot of firepower, so you don't know when he's going to unleash a forehand or backhand.

"He can serve well too, so I am going to have to be sharp at my end with everything, focus on being aggressive when I have the chance, and play my game."

Monfils is one of the great players to watch in men's tennis and he will probably be the crowd's favourite in Auckland tonight.

Haas says he likes to see entertaining players when he's watching from the stands but doesn't really take notice on court.

"When I am a spectator I like the fact that you see some emotions," he said.

"But when I am on the court I never look over to the other side and see what they're doing, because I am so focused on what I'm doing.

"But you do try to sometimes get players frustrated and get them to a point where they're thinking too much.

"Also you can play a certain game where they don't know if you're going to be aggressive, keep the ball in play or come into the net.

"These are the sorts of things that sometimes rattle your opponent and get them thinking.

"Hopefully I get a few moments where he'll panic a bit."

Meanwhile in the evening matches yesterday Spanish top seed David Ferrer started his defence of this title by beating Lu Yen-Hsun from Taiwan 6-4 2-6 6-3, and in the final match the New Zealand doubles duo of Rubin Statham and Artem Sitak went down to Johan Brunstrom from Sweden and Denmark's Frederik Nielsen 6-3 6-2.

- © Fairfax NZ News