Major takeaways from Tottenham 0-1 defeat to Ajax in the Champions League semi-final first leg

Ajax Amsterdam took a massive stride towards a first Champions League final for 23 years as Donny van de Beek's early goal earned a 1-0 win at Tottenham Hotspur in the first leg of their semi-final. 

Here are major takeaways from the clash at the Tottenham Hotspur Stadium. 

Speaking ahead of the first leg, Tottenham boss Mauricio Pochettino challenged his players to "set your dreams to infinity and beyond" as he looked to lead the club to their first European Cup final.

But Pochettino's amusing decision to reference the catchphrase of Toy Story character Buzz Lightyear wasn't the most significant of his pre-match comments.

Complaining about Tottenham having to play West Ham on Saturday while Ajax benefitted from having their domestic match postponed, Pochettino admitted his players looked "stressed and fatigued" during the 1-0 defeat against West Ham.

The introduction of Moussa Sissoko as Vertonghen's replacement gave Tottenham more bite, but it wasn't enough to stop the north Londoners crashing back down to earth.

With top goalscorer Harry Kane injured and South Korea forward Son Heung-min suspended, Tottenham were painfully short of quality up front.

Kane and Son were watching from the stands as Brazilian Lucas Moura started alongside Fernando Llorente in Tottenham's attack.

But neither understudy was able to do a convincing imitation of their absent team-mates and Tottenham were fatally undermined as a result.

It didn't help their cause that Christian Eriksen and Dele Alli, Tottenham's two playmakers, were well below their best as well.

Trailing in the first half, Llorente, unmarked and just eight yards out, had a golden chance to equalise when he headed woefully wide.

Llorente was targeted with a flood of long balls and crosses as Pochettino tried to bludgeon Ajax into submission, but the Spaniard got little change out of Ajax's well-marshalled defence.

Lucas was even more anonymous and Tottenham will welcome Son back with open arms for the second leg.

Christian Eriksen admitted Tottenham were well below their best against Ajax. Denmark playmaker Eriksen was one of many Tottenham stars who failed to shine on the night and he conceded it was far from their best display.

"We were under-par, we didn't play our best at all. In the first 20 minutes, we were ball-watchers. We need to change it up a lot for the next game," Eriksen told BT Sport.

"We made them look a lot better. They are a good side, but we helped them along the way. It was our fault. We were better in the second half.

"No one wanted to play the first half we did. Everyone knew we didn't compete. We still lost, but we were better in the second half."

Mauricio Pochettino took his share of the blame for "sloppy" Tottenham admitting he used the wrong tactics.

Pochettino's side made a dismal start as Donny van de Beek put Ajax ahead after just 15 minutes at the Tottenham Hotspur Stadium on Tuesday.

Pochettino completely changed his game-plan by switching from a 3-5-2 formation to a 4-4-2 system.

Pochettino conceded he had blundered with his game-plan, but the Tottenham manager was also angry with the lethargic way his players started the club's first European Cup semi-final for 57 years.

"Watching now of course I can accept it was a mistake the shape we used. But there were not too many options," Pochettino told BT Sport.

"I am not happy. But our lack of energy from the beginning made our game difficult. We were a little sloppy.

"It was not the shape that conceded the goal. Our approach to the game was not good. I am the manager so I have responsibility."

Ajax Amsterdam coach Erik ten Hag praised his young lions after the win. 

"A fantastic achievement. We fought like lions," Ten Hag said. "We are halfway there and in good shape. The willpower was very nice to see."

Had David Neres not been denied by the post late on Ajax's position would look impregnable, but Ten Hag knows the job is not yet completed.

"I think it's an excellent result for us. We won the game. We are satisfied. We have a very good starting point, but we're only halfway through," he told reporters.

"We can play football in different styles. We can defend very well. We have a team that works together really well; they can fight together really well."

Ajax are four-time European champions with a rich history of producing some of the continent's finest players and, on the evidence of this mature display, their latest crop of wonderkids are worthy successors to Johan Cruyff, Marco van Basten, Patrick Kluivert and Dennis Bergkamp. 

The average age of Ajax's starting eleven in the Champions League this season has been 24 years and 257 days, with their line-up against Tottenham the youngest of any Champions League semi-finalist for the last six years.

But any thoughts that the Dutch club might be gripped by stage-fright in their first Champions League semi-final since 1997 were quickly erased.

Surprise wins over Real Madrid and Cristiano Ronaldo's Juventus in the knockout stages had announced Ajax's as Europe's most coveted rising stars.

Once again they rose to the challenge, capping a superb start by taking the lead in the 15th minute when Donny van de Beek's cool finish survived a VAR review.

With Frenkie de Jong, who has already agreed to join Barcelona next season, dominant in midfield and Ajax's 19-year-old captain Matthijs de Ligt, who wasn't born when they last reached the semi-finals, imperious in defence, the visitors were able to weather a Tottenham revival in the second half.

A Champions League journey that started for Ajax in the qualifying rounds in July and August could be about to culminate in a final appearance in Madrid 11 months later.