(Reuters) - Real Madrid will turn up with a better attitude for the local derby with Atletico Madrid on Saturday after needing a stoppage-time penalty to squeeze past promoted Elche 2-1 in midweek, said coach Carlo Ancelotti.

The Italian was not happy with his team's performance on Wednesday and knows they need to make a drastic improvement against Atletico who have a maximum 18 points from their opening six La Liga games.

"Atletico are more aggressive than we are, they have more physical strength, but I think Real Madrid have more quality," Ancelotti told a news conference on Friday.

"Tomorrow we are going to play with a different spirit," he added, referring to the game at Elche.

Ancelotti's remarks were echoed by Real goalkeeper Diego Lopez.

"We cannot allow any slip-ups, even more so in our own stadium," said Lopez.

Third-placed Real, two points behind Atletico and Barcelona at the top of the table, look certain to hand world record signing Gareth Bale his home debut.

The Wales winger, who cost 100 million euros ($135.42 million) when he left Tottenham Hotspur at the start of the month, was due to play at the Bernabeu for the first time against Getafe last weekend but tweaked a thigh muscle in the warmup.

Bale was then rested for the unconvincing La Liga victory over Elche.

Atletico have an undistinguished recent record against their derby rivals.

The 2-1 victory in last season's King's Cup final was Atletico's first win over the nine-times European champions for 14 years.

"We will have to play at 110 percent," said visiting coach Diego Simeone. "They are better than us and have an excellent team."

The Madrid derby starts at 2000 GMT while Barcelona kick off at fourth from bottom Almeria at 1600.

(Editing by Tony Jimenez)