Mauricio Pochettino says it is highly impressive that Dele Alli has improved his goalscoring contribution this season despite losing the element of surprise and becoming a marked man.

Alli enjoyed a stunning breakthrough campaign last term, making the step up from League One to the Premier League with consummate ease, scoring 10 goals for Spurs and ending up as a key member of the England squad that headed to France for the European Championship.

While the 20-year-old has had dips in form since the summer, he has scored three times in his last two games, taking his tally to seven goals for Spurs so far this season – three more than he had at the same stage last year.

Meanwhile, Alli’s record of 16 goals in his first 50 Premier League appearances compares very favourably with some legendary goalscoring midfielders from yesteryear - David Beckham managed 11 goals in his first 50 top-flight matches, while Frank Lampard and Steven Gerrard mustered five efforts and two strikes respectively.

“He’s at a very good level,” said Pochettino. “If you compare with this type of player, who were great, fantastic players, he needs to keep going in this way because he’s showing now he can be one of the best players in England.

“It’s the toughest and best competition in the world. If you’re one of the best in England then you’re one of the best in Europe.

“He’s growing up, not only in football but as a person. For different reasons and different problems, he’s improved a lot in his behaviour and game. Now it’s a huge challenge for all our opponents to try to stop Dele Alli, when at the beginning, one and a half years ago, he was a surprise for people, which is very different.

“Is he our best ever bargain? Tottenham were right in the moment that we signed him - it was a very important deal for the club and he’s one of the best. Over the years Tottenham have had Gareth Bale, Luka Modric, Dimitar Berbatov and different players but it’s true it was a very good deal when we signed him.”

Former Spurs midfielder Jamie Redknapp has suggested Alli is already a £50million-plus player”, and Pochettino said: “Why not? He’s right in his opinion.

“Dele Alli is showing a quality and talent that is difficult to find in Europe in a 20-year-old, so why not? I don’t know if now but maybe yes, one day.

“In his head, he wants success here. He’s very happy here and there’s no doubt he wants to win titles here. I’m very honest in that situation.

“He’s always doing jokes on the training ground or in the dressing room, but he’s very serious, too. I hear him say all the time ‘I want success here, I want to lift trophies here’.”

Pochettino will hope that Alli adds to his goal haul at Watford on New Year’s Day and that Spurs are able to bank their sixth victory in seven games.

However, the manager is being forced into a defensive reshuffle after losing both Kyle Walker and Jan Vertonghen to suspension.

Walker will be missing from the starting line-up for the first time in eight games, while left-back Danny Rose has started the last seven consecutive matches.

The pair have been in fine form, contributing a goal and four assists between them in Spurs’ last three outings, and Pochettino admits that is one reason why he has recently not rotated his full-backs as much as he has done in the past.

“Maybe for different reasons,” he said. “Ben Davies was injured and Kieran Trippier was a dad [earlier this month] and struggled to manage his life because his little boy finds it difficult to sleep at night.

“It’s different reasons, and then it’s true that our full-backs Kyle and Danny have showed a high level - and with our gaps in between games that we’ve have, maybe it has given us time to recover. You can give them the possibility to play again.

“I’m happy with Tripper and Davies and maybe they will have the possibility to play in the next few weeks.”

Pochettino used a three-man defence and wing-backs for the first time at Watford last December, and he is considering using the same set-up this time. “Maybe,” he said. “The good thing is that we’re working every week - every time we have time - and the players now feel comfortable to play in different ways, with three or four at the back. That’s a very good thing for us.

“We need to assess different options and how we replace Jan Vertonghen and Kyle Walker and then we see how they (Watford) play. Tomorrow we will decide if we play with three or four.”

Follow me on Twitter @BenPearceSpurs