Showing their first signs of vulnerability, cup-holder Barcelona visit Malaga on Thursday needing to overturn a 2-2 draw to advance in the Copa del Rey and set up a likely semifinal with Real Madrid.
After strolling through the first half of the season, Barcelona has suddenly stumbled in consecutive games and faces its first must-win match of the campaign.
Madrid visits Valencia the day before, holding a 2-0 advantage from the opening leg played last week. Jose Mourinho's squad also demolished Valencia 5-0 in a league match on Sunday.
On the other side of the bracket, Atletico Madrid is at Real Betis on Thursday aiming to protect its 2-0 first-leg victory. Sevilla hosts Real Zaragoza on Wednesday after they drew 0-0 in their first meeting.