Sporting Life - Wimbledon 2008

Defending champion Roger Federer insists he will not be under-estimating big serving Croatian Mario Ancic in the quarter-finals at Wimbledon.

Ancic is the last man to beat Federer at SW19 having knocked out the Swiss in the second round back in 2002.

And the world No.1 claims that defeat has taught he a valuable lesson - with Federer determined not to suffer the same fate again.

Federer said: "I completely underestimated him back in 2002 when I played him. I got completely surprised.

"He played well until the very end. I was a little shell-shocked and I didn't know what happened to me.

"It taught me not to under-estimate any opponent, no matter where they're from, what technique they have, what ranking they have. It's just a matter of going out there and putting it all together and giving 100 per cent."

Federer has already gained his revenge over Ancic, having won their five encounters since that defeat in 2002.

And Ancic, who reached the last eight after a five-set epic against Fernando Verdasco, knows that he will face a completely different Federer to the one he beat six years ago.

Ancic admitted: "I can sit here and tell stories about how great the win was and how I beat Roger, but actually it wasn't Roger Federer as I know him today. I think we are both six years better players.

"He was the up-and-coming top-10 player who was at that moment struggling in grand slams. I think from the year after when he won Wimbledon, he exploded, and today he's a completely different player."