Mauricio Pochettino said it, late on Sunday afternoon in the press conference room at White Hart Lane. Eric Dier, speaking at the same time out in the car park, said exactly the same thing: that Vincent Janssen has improved beyond recognition in the last few weeks.

It is no exaggeration to say that one month ago Janssen’s Tottenham career looked finished. He was left out of the 18-man squad for the Europa League first leg at KAA Gent, and when Pochettino was asked why afterwards, he pulled no punches. “He needs to show more,” Pochettino said, “it is about how [the players] show their quality, their belief, on the training ground.”

Three days after that Janssen was back on the bench for an FA Cup tie at Craven Cottage. Spurs went 3-0 up with a Harry Kane hat-trick and even then Janssen did not get on. He got one minute against Gent in the second leg but the following Sunday, against Stoke, Spurs were 4-0 up at half-time. Again, Janssen did not get on.

Fast-forward two weeks though and something has changed. Janssen came on with 16 minutes left on Sunday afternoon and, contrary to all expectations, he scored in open play. He has scored four penalties but this was his first not from the spot. He has started 10 games and made another 20 appearances from the bench.

Everyone at Tottenham was delighted for Janssen after his goal and both Pochettino and Dier were on the same page when discussing it afterwards.

“All the squad and the team-mates are really happy [for Vincent],” Pochettino said. “Of course [it can be a turning point]. I have told you that in the last few months he has stepped up and started to work better, and I was happy in the way he was performing in training. In football you need to be ready to show your quality.”

That is what Pochettino had criticised Janssen for failing to do in the past, for not showing the conviction and confidence required to play up front for a top club. He has clearly found the adjustment hard from AZ Alkmaar to Spurs, not just the mentality but also the speed of the game, which often looks to pass him by in the Premier League.

But his team-mate Dier was just as upbeat after the game about Janssen’s recent improvement, saying, just like Pochettino did, that there had been a big change noticeable behind the scenes.

“It is tough coming from a different country, I don’t think people realise how tough it is,” said Dier, who signed for Spurs from Sporting CP in the summer of 2014. “Especially if you look at where Vincent has come from in such a quick period of time; from where he was and where he is now. He is just adapting to everything. Everyone was obviously delighted he scored the goal, I'm really happy for him and hopefully he can score more now.”

Supporters clash ahead of Tottenham's FA Cup match against Millwall Show all 10 1 /10 Supporters clash ahead of Tottenham's FA Cup match against Millwall Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans There was a heavy police presence at White Hart Lane ahead of the FA Cup match between Tottenham and Millwall. AFP/Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans Millwall fans arrived at the ground surrounded by police. AFP/Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans Hundreds of police officers lined the streets. Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans A video later emerged online purportedly showing one Spurs fan being punched in the face by a Millwall supporter. AFP/Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans The London derby took place amid a backdrop of heavy police presence. Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans A flare is let off outside the stadium. Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans The Metropolitan Police helped the match to pass without serious incident. Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans Inside White Hart Lane, all stewards wore plastic hard hats. Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans Millwall sold out their ticket allocation for the match in minutes. AFP/Getty Images Supporters clash ahead of Tottenham's FA Cup match against Millwall Trouble flares between Spurs and Millwall fans And the game was marred by racist abuse directed at Spurs forward Son Heung-min. Getty Images

If Janssen has started to train with more conviction and belief, and if he has started to grow used to the pace of the Premier League, then that could be a crucial resource for Spurs over the final straight this season. With Harry Kane nervously waiting for a scan on a badly twisted ankle, Pochettino knows that he will have to call on Janssen and Heung-Min Son up front over the next few weeks. Son has a better record this season but Janssen gives them a different option up which could be just as useful.

Spurs scored six goals after Kane went off on Sunday but their next opponents will be harder, especially with an FA Cup semi-final and a north London derby coming up next month. This injury to Kane could throw their season off course unless Son and Janssen can rise to the occasion. Dier certainly hopes that they do.