Cristiano Ronaldo's header has given Real Madrid a 1-0 half-time lead over Schalke 04 in the first leg of their Champions League last-16 tie in Gelsenkirchen.

Chances were difficult to come by in the early stages as both sides struggled to find their passing rhythm, but Schalke looked comfortable sitting deep to defend against the holders.

A clever piece of play from Eric Maxim Choupo-Moting created a decent opening for his side as the hosts moved the ball across the edge of the box quickly to pick out Dennis Aogo, whose effort sailed over the crossbar.

Schalke forced Iker Casillas into the first meaningful save of the match when Klaas-Jan Huntelaar dropped deeper to collect the ball before testing the Spaniard with a powerful low effort.

Roberto Di Matteo's side were made to pay for not making more of a promising start as Ronaldo put his side ahead by finding space in the box to head home from Dani Carvajal's cross.

Karim Benzema could have doubled the lead moments later when he timed his run perfectly to collect a clever through-ball from Toni Kroos, but Timon Wellenreuther made an important save with his feet.

Schalke's goalkeeper came to rescue once again to get a vital hand on a swerving free kick from Ronaldo.