Mauricio Pochettino believes that Mousa Dembele proved his "genius" during Tottenham Hotspur's 1-0 victory over Arsenal but admitted he must manage the fitness of the Belgium international for the rest of the season.

Dembele endured a slow start to the campaign having struggled with a series of fitness problems since the end of last term.

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But the Belgian has impressed in recent key games against Manchester United, Liverpool and Arsenal to help Tottenham secure seven points from a possible nine to move them up to the third place in the Premier League table.

Harry Kane grabbed the headlines in the north London derby after scoring the winning goal in the 49th minute

But Pochettino also hailed Dembele's performance with the midfielder running the show from the middle of the park in the absence of Harry Winks.

"Yes. I think last season he played so well, and then at the end of the season he suffered a problem in his ankle, struggled during pre-season and now is again feeling good," Pochettino said as quoted by Football.London following the 1-0 win over Arsenal.

"I think the problem is about his fitness, no? Because, that is about his quality, there is no doubt that like I have told you many times, for me he is a genius, and unbelievably player. But we must be careful about his fitness, it is good and he can train and, he can make this type of performance because he is a great talented player."

Pochettino was a happy man in the press conference but still was left fuming when asked why he left Dembele's compatriot Toby Alderweireld out of his squad to face Arsenal.

The Belgium centre-back returned to action during the Wednesday's victory over Newport County in the FA Cup after recovering from a hamstring injury which had kept him on the sidelines since the 3-1 victory over Real Madrid on 1 November.

Alderweireld played the full 90 minutes of the game but Pochettino still opted to leave him out of the squad to face Arsenal, retaining Davinson Sanchez and Jan Vertonghen in the heart of the back-line.

"Sorry? After the game I need to explain this? You think I need to explain why I picked one or another? Why? Sorry, I don't understand your question. Why I pick 11 players? Because I need to pick 11 players. I don't understand your question," the Tottenham boss stated.

"I picked a player that I believe are the best to play in every game, but, if I explain why I don't play Alderweireld, I need to explain why for Danny Rose, Wanyama, Llorente, Michel Vorm, Harry Winks - I don't understand your question,"

"The reason is that I believe the 11 players that played today were the best to win, we won, if we lose maybe I accept the question, because I was wrong in my selection. But after three points, I think the question....

"I don't take like a criticism, it is your opinion. He played like different players against Newport, and the decision was be out of the squad. But that is, sorry, the club, Daniel Levy pay for [me] to make decision, not to make happy the people."

Mauricio Pochettino
Pochettino. Getty Images
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