Mauricio Pochettino hailed Dele Alli as the best young player in Europe after Tottenham Hotspur's 4-0 win over Watford on Saturday and described the midfielder as like a "son."

Alli, who turns 21 on Tuesday, scored a stunning opener in Tottenham's win at White Hart Lane, taking him to 16 Premier League goals for the campaign and 19 in all competitions.

The England international has now been involved in 40 Premier League goals since joining Spurs from MK Dons -- the same number that Frank Lampard, Steven Gerrard and David Beckham had managed combined before their 21st birthdays. Cristiano Ronaldo had been involved in 25 -- 14 goals and 11 assists -- by the time he turned 21.

Informed of the comparisons, Tottenham manager Pochettino told reporters: "Wow. That's unbelievable. He's green but he's great. First of all, he's a great kid, a lovely, lovely person. And then he is a great player."

Asked if Alli is the best young player in Europe, Pochettino said: "I think today, his age and with his stats, I think so. If not he's the best, he's one of the best for sure.

"He is so young, he can improve a lot, learn a lot, his potential is massive. Every day he's improving, and getting more mature. He's improving in his skills but in his character as well.

"He's special. He's different from all the players who play now at his age. He's so experienced. His energy, his character, his quality. He is a unique player."

Dele Alli scored an impressive opener against Watford on Saturday. Dan Mullan/Getty Images

Alli's temperamental character remains the only question mark about his game but he has responded superbly to the first red card of his career against Gent in February, scoring in six of the seven matches since.

After the 2-2 draw at Wembley, which saw Spurs exit the Europa League, Pochettino defended Alli, and he said his decision has since been justified by the player.

"People criticised me for different reasons, tried to 'kill' me and him, but time has shown we were right to support him, to give him love because he is so young," he said. "His character is perfect for a player; when you feel that to lose on the pitch is like losing your life.

"Of course he is young and needs to improve, but he needs love, not to be punched or punished. I am so happy for him because I knew the relationship from day one was tough. It was friendly, lovely, but tough too because it's like when you have your son, you love him, but sometimes you have to be tough."

Pochettino also praised Tottenham chairman Daniel Levy for his part in turning the club into title contenders.

"We had a difficult relationship at the start but we built a strong one," Pochettino said of Levy. "He deserves a lot of credit. Tottenham are growing up and if I am doing well, it is because he believed in me and brought me here."