West Ham United boss Sam Allardyce says Harry Kane needs to prove himself no flash-in-the-pan.
Kane and Tottenham will meet West Ham this weekend.
"He's been so brilliant," Allardyce said, "but he's not that well known in the Premier League. It's similar to Enner Valencia and Diafra Sakho at West Ham this season. Because they're unknown they can surprise defenders. They've not been able to watch them play.
"The test of time, if they will be great, is when everyone knows how they play if they can sustain it then. That will be the test for Kane."
