Gelsenkirchen: Manchester United goalkeeper Edwin van der Sar says that fellow veteran Raul must be closely watched if United are to avoid defeat against Schalke in the Champions League semi-finals.
The sides clash in the first leg at Schalke's Veltins Arena on Tuesday, where Raul will be looking to add to his record tally of 71 goals in the competition.
The wily former Spain international netted in both legs of Schalke's shock 7-3 aggregate defeat of holders Inter Milan in the previous round and van der Sar knows that he is capable of changing a game in an instant.
"Raul is quite an amazing player," said 37-year-old van der Sar, who will retire at the end of the season.
"He played so many years at Real (Madrid) at a high level and all the goals he scored in the league for them. And top scorer in the Champions League.
"You can't let him out of your sight. He only needs a little chance to score a goal, so our defenders should be on their toes against him."
At 33 Raul may still have more Champions League campaigns ahead of him, but van der Sar knows that next week's second leg at Old Trafford could prove to be his own last ever game in the competition.
The former Dutch international has already tasted Champions League success twice - with Ajax, in 1995, and with United, in 2008 -- and is poised to Claude Makelele on a record 13 semi-final appearances.
Van der Sar's penalty save from Chelsea's Nicolas Anelka secured the 2008 trophy for United and he says it is the prospect of further silverware that keeps him going.
"I'm just enjoying it," said van der Sar, who is seeking his 50th clean sheet in Europe's top club competition.
"It's always nice to be involved in a winning team. We've done well lately and hopefully we can keep going.
"I've had a reasonable career so far and hopefully we can finish it off nicely."