The former Arsenal and Tottenham defender says players have to string together five, 10 or even 15 years at the highest level to be considered among the best
Sol Campbell has called on Dele Alli to prove his consistency before he can be considered a world-class player.
Alli has scored seven goals for Spurs so far this season and was on target in his England debut against France in November.
It has been a rapid rise for the 19-year-old, who signed for Spurs in January 2015 before going back out on loan to former club MK Dons, but former Arsenal and Tottenham defender Campbell wants to see at least five years of quality performances from the midfielder.
"He does look a real prospect, but it is very early stages for him," he wrote for Sportlobster. "I don't really want to know about a player until five or six years down the line and I can see their consistency.
"Anyone can have a good season or two - I want to see five, 10, 15 years of quality from a player to be able to call him 'world class'.
"We have seen players light up this league before for two or three years and then drop off and fade away. I am not saying Dele Alli will do that, but he needs to keep going.
"Hopefully he has a good mentality that will allow him to have the same sort of career [Steven] Gerrard and [Frank] Lampard enjoyed in the Premier League. It would, of course, be great for England if he could."
- Goal