Alderweireld injury a blow to Spurs, but opportunity for Sanchez and Dier
Given the fees paid for defenders in the last couple of years, the £11.5 million signing of Toby Alderweireld is surely one of Tottenham's best-ever deals.
Spurs conceded 53 goals in the 2014-15 season, but after the Belgian's arrival that figure plummeted to 35 in 2015-16 and then to just 26 last term.
Like the best centre-backs, Alderweireld is not just a fine defender in his own right; he also makes those around him better. He can certainly play a bit, too, and his move to the right side of Spurs' back three has enabled him to bring the ball forward more.
It was probably not a coincidence that Alderweireld's absence through injury last autumn coincided with Tottenham's worst run of the season. He was certainly missed for the successive 2-1 defeats away against Monaco and Chelsea in late November in particular -- both damaging losses in the context of the season.
Twelve months on, the 28-year-old is now facing another spell on the sidelines at a similar juncture, having pulled a hamstring against Real Madrid.
The signs of fatigue were there in the previous two matches when he was unusually beaten to three headers against West Ham and Manchester United, two of them resulting in goals and the other hitting Hugo Lloris' post. His injury is certainly a blow, yet it provides an opportunity to see whether Spurs are better able to cope without him this time, to assess both Davinson Sanchez and Eric Dier as centre-backs without the help of their influential colleague.
Sanchez has fitted in well thanks to his valuable combination of pace and strength, but naturally he lacks Premier League experience, so he is prone to the odd mistake and sometimes looks vulnerable in the air.
Nonetheless, Spurs' only defeats since the Colombian's £40m arrival have come when he was sitting on the bench -- against Manchester United and West Ham.
That speaks highly of his ability, but he has been well protected, operating between the experienced Alderweireld and Jan Vertonghen while also standing between Tottenham's hard-working midfield and sweeper-keeper Lloris.
Now though, after Alderweireld's injury, Sanchez has been moved to the right side of the back three -- a rather different task -- and Crystal Palace threatened down his flank on a few occasions last weekend. He might find himself more exposed, and Spurs' two wide centre-backs are also expected to be involved in the build-up play -- Vertonghen does this well on the left -- so the new recruit's ball-playing ability may be tested more as well.
Meanwhile, Dier is set for a run in the centre of the back three and has a chance to prove he is as equally comfortable there as in midfield, which some doubt. He has made mistakes at centre-back in the past and it seemed his future lay in front of the rear guard, but Pochettino has a different perspective.
The Argentinian states in his new book: "Eric thinks he's further ahead as a midfielder than as a defender. We had a long chat about that because I disagree. I've told Eric he has what it takes to be the best English centre-back but he has to be convinced of that himself."
Dier appears to have responded and, while stationed in defence, has been one of Spurs' best players in the last three games against United, Real Madrid and Palace. He has kept pace with speedsters such as Marcus Rashford and Wilfried Zaha and thrown himself into trademark, crunching, sliding tackles.
There have still been errors -- most obviously when he allowed United's Anthony Martial through to score the winner at Old Trafford. But cut out such mistakes and Dier could not only underline his importance to Tottenham, he could also strengthen his position with England.
The assumption has been that the 23-year-old is going to be a long-term midfielder for the national team, and that he therefore needs practice in that role for his club. Yet England boss Gareth Southgate is intending to use a back three ahead of the World Cup and has just omitted Chris Smalling from his squad because he wants centre-backs who are comfortable on the ball. He has also made Dier captain against Germany, underlining his importance.
"We have players like [John] Stones and Dier and [Harry] Maguire who are even better," Southgate said.
With Spurs' own Harry Winks looking an increasingly attractive option for England, offering technical qualities that few of his countrymen can, Dier now has increased competition in midfield with the Three Lions.
Yet Southgate's desire to play with three ball-playing centre-backs might give him a new role for his country, ironically in the very position he was trying to move away from. And, while Alderweireld's injury is unfortunate for Spurs, it gives Dier a chance to develop some consistency as a centre-back while additionally handing Sanchez new challenges in a wider position.
If the pair can pass the tests ahead and ensure Alderweireld is not too greatly missed, it will only underline Tottenham's progress and their ability to cope without key players.
Ben is ESPN FC's Tottenham blogger. Follow on Twitter: @BenPearceSpurs.