The Englishman has struggled to impress since joining Everton from Tottenham in January.
Writing his column for The Mirror, Collymore said: "Dele needs to answer some serious questions, for himself, no one else. He has to ask: Do you want to play professional football, or are you not cut out for it?
"Dele Alli may decide he doesn't love it anymore. Go and find something you are passionate about, and don't cheat the game by going on a circus around other Premier League clubs.
"He'd be cheating the fans and clubs and managers of those clubs. He's gone from the next golden midfielder in Europe, to people asking if he is still a Premier League player. The answers can only come from Dele.
"Look in the mirror and be honest: Do you want to be a pro or not? Don't drift for another five years because that would be a crime against his ability."
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