Atletico Madrid manager Diego Simeone has insisted that Real Madrid have improved since he led his side to a 1-0 league victory over their rivals in September.
Simeone's team take on Carlo Ancelotti's men on Wednesday night and the Atletico boss expects a much tougher test in the Copa del Rey semi-final first-leg.
"When we faced Madrid, in week six of the league, they'd had very few games with their coach," Simeone told reporters.
"They've got better and have developed a 4-3-3 that works well for the attackers they've got. There's no doubt they're better now."
Real Madrid have not lost in any competition since the end of October.