Barcelona goalkeeper Victor Valdes says Chelsea would be wasting their time trying to man-mark Lionel Messi.

Barca are at Stamford Bridge for the first-leg of their Champions League semifinal.

Valdes warned: "Messi is No 1 in the world - that's unquestionable. Every rival fears him but if you develop a system to stop him, that makes it better for his fellow strikers and that's a big advantage for us.

"To stop Leo is always very difficult because he is incredible in every game and scores so many goals."