But the White Hart Lane idol is backing Spurs' playmaker to return to the level that won him a string of England caps.
After netting 18 times in the league for Spurs last season, Alli has struggled to replicate his goal threat this campaign, and has just three Premier League strikes to his name so far, his last goal coming in Spurs' win over Liverpool at the end of October.
Tottenham manager Mauricio Pochettino decided to leave the 21-year-old on the bench for the win over Brighton on Wednesday, but King says Alli has the talent to bounce back.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"Dele is just a young player, and young players are going to have a dip in form, especially attacking players," King told Reuters in an interview.
"When you play in the number 10 role, it can be difficult to be consistently good. You see that with wingers, too.
"He doesn't strike me as someone who feels the pressure. He just goes out and plays his game. Now he is a marked man because of how much ability he has got.
"I remember watching him at MK Dons (Alli's previous club), and you could see he was a player who was destined for the top then. Having been around him now, I can see he has the confidence to get there.
"He will figure it out -- all the top players do. He is still putting in the work for the team, and as long as he is putting in the work on the training pitch, then he will come out of it, no problem."
The 2-0 success over Brighton was Spurs' third home win in a week, and the three points moved Pochettino's side back into the top four.
WEMBLEY HOODOO 'GONE'
King, who represents Spurs in an ambassadorial role, believes such a run proves that the team have got over their initial problems at Wembley when they managed only two wins in their first 12 games at their temporary home.
"The Wembley hoodoo is firmly gone now," he said. "It takes a while to settle in. Everything is a bit different. Even for the fans it is different.
"You expect a few hiccups moving into a new stadium, but the team are over that now. They have put in some good performances - Dortmund, Real Madrid, the Liverpool game - and then Stoke on the weekend was another great performance, scoring five goals."
In the aftermath of the Brighton win, with runaway Premier League leaders Manchester City up next at the Etihad Stadium, Pochettino proclaimed that Tottenham would "go to Manchester to win".
City remain in imperious form, having earned a Premier League-record 15th consecutive win when they beat Swansea City on Wednesday, maintaining their 11-point lead at the top of the table.
But King says the title race is not over yet.
He believes that in Harry Kane, Spurs have one of the best strikers in the world who can cause City problems.
"People are looking at this Christmas period and hoping that City slip up. Then if they do slip up once, how will they react?
"I have been around in this league long enough to know it only takes a few bad results and the picture changes."
King added: "When you talk about the best strikers in the world you always talk about (Cristiano) Ronaldo and Lionel Messi, but after that Harry Kane is right up there, especially in terms of (a) number nine.
"For me, (City's) Sergio Aguero was the best striker in the Premier League, but I think that Harry has overtaken him now.
"Right now, I wouldn't swap Harry for anyone. If he plays well, Spurs have every chance against City."
(Editing by Neville Dalton)
