Tottenham Hotspur's season went from bad to worse this week after they crashed out of the Europa League by Dinamo Zagreb.

It follows on from their exit from the FA Cup whilst, in the Premier League, the north Londoners find themselves in eighth place, six points behind the top four.

A lot of Jose Mourinho's problems lie in defence. Seemingly every week, he's left to rue individual errors at the back, and that much can be seen in just how constantly he's chopped and changed his back line.

Centrally, all of Eric Dier (21 league starts), Toby Alderweireld (18 starts) and Davinson Sanchez (14 starts) have been rotated often and, similarly on the right, it seems as if Mourinho can't decide between summer signing Matt Doherty and Serge Aurier, who we know all too well can be a liability at times.

In amongst all the mediocrity, there is one silver lining for Spurs - Sergio Reguilon.

Their embarrassing departure from the Europa League in midweek merely highlighted just how good the Spaniard is - as we outlined in this article earlier in the week, Ben Davies is just not good enough to start for the club anymore.

Aside from Harry Kane and Heung-min Son, Reguilon is actually a major source of goals for Mourinho and, in his absence last month, Spurs endured their worst run of the season, losing four of five league matches.

Indeed, only the electric attacking duo have contributed more assists than the former Madrid star (three), whilst his ability to get forward is shown by the fact that he's averaged one shot per game each league outing.

By comparison, Steven Bergwijn (0.8), Tanguy Ndombele (0.6) and Lucas Moura (0.6) are all averaging fewer attempts despite often playing right behind the striker, as per WhoScored.

Speaking about the move to sign him back in October, football.london reporter Alasdair Gold waxed lyrical, saying:

"You kind of don’t want to overshadow Sergio Reguilon, who I think is going to be one of the best left-backs in Europe – probably almost is. With Sevilla, he was phenomenal: had a great season, won the Europa League. He’s got incredible confidence. He’s come straight into the group and everyone loves him."

Over the past 18 months or so, a small problem was building at left-back - on top of the doubts over the Welsh international, the long-serving Danny Rose wanted out of the club and reportedly had a bust-up with Mourinho.

As a result, he was omitted from all of Spurs' squads and has not featured since he returned from a loan spell at Newcastle United.

When Reguilon became available, Daniel Levy acted quickly and the move came out of the blue, costing the club around £32m, as per Sky Sports.

"Reguilon has grown at a barbaric rate. He's a much more complete player than when he first joined. Hopefully, he can continue with us," said Sevilla boss Julen Lopetegui.

This has undoubtedly been a steal for Spurs, even if there's a buy-back clause within the contract, something which may not even be triggered given the array of options Zinedine Zidane has at his disposal.

Alongside Pierre-Emile Hojbjerg, he has arguably been their player of the season thus far and everyone in N17 has Levy to thank for that. He didn't have to open his wallet on top of a £30m splash on the Dane and Matt Doherty, but he did.

The Spurs chairman has once again displayed his genius in the transfer market and despite all of the lows right now, he'll be glad he pulled the trigger on Reguilon, who is now already valued at £45m by CIES.

AND in other news, Mourinho surely seething with £18m-rated Spurs star after shocking Zagreb showing...