"If you are in a team not believing you are the better team, or the better player, you are not going to win one game. A team without egos is definitely not a good team," Muller said.
His remarks came after Waratahs flanker Ben Mowen's comment this week that a team like the Sharks with egos "can be rattled". Muller, a Springboks second-rower, believes his side has the credentials to walk tall and proud, as it does. He also says that they must do so to win the Super 14.
"Some people call it ego. Some people call it experience. And some people will probably say something nasty about it. But I think it is really important," Muller said. "Probably five or six guys in the squad played in the World Cup final, the Currie Cup final and the Super 14 final in 2007 and semi-finals last year. From all these experiences you definitely learn something.
"This [Sharks-Waratahs] game is a final. If we want to be the best we have to win four weeks in a row. The one that loses [on Saturday] is probably very close to being out of the running."
Muller said running on before near-capacity crowds at their home ground helps to stir passion in the players.
"[Playing before] 35 to 42 000 people every Saturday is something special," he said. "It is hard to explain, but when you run on and see that stadium full it makes a big difference."
Muller believes the Sharks, placed fourth on 35 points, and the fifth-placed Waratahs on 32 points have ridden a similar journey towards this crucial round-13 fixture. But Muller agrees the Sharks, early competition leaders, have shown signs of mental weakness under pressure and that was highlighted by their losses to the Crusaders and Cheetahs. But he attributes that more to the fatigue of playing 10 straight games, the long distance travel and varying time zones.
"After all that hard work overseas, winning three out of four and coming back, we let it slip a bit," Muller said. "Our loss to the Cheetahs and Crusaders were two mighty blows for us. The same happened to the Waratahs. They lost two games [to the Bulls and Force] before their bye.
"It takes a lot on the body and mind to have 10 straight weeks of games. Having the bye so late was really against us and the Waratahs. You get so tired you forget to do the small things. We did let ourselves down a little bit. We are still in the running. But if you lose this weekend, you could end up ninth. Or, if you win, you could end up first."
Last year the Sharks lost to the Waratahs in the regular season and in their semi-final. "We got embarrassed twice last year by the Waratahs," Muller said.