The England midfielder is the driving force behind Carlo Ancelotti's side's success - they are a far weaker side without him.

It was assumed, for some time, that in Vinicius Jr and Kylian Mbappe, Los Blancos had pretty much all they needed to swat opponents aside. Midfielders come and go, but world-class, Ballon d'Or-contending, match-winning forwards are almost unique.

As it turns out, football is more complex than that. A look at the past couple of months has shown that Madrid can live with a suspended Vinicius, can cope with an injured Rodrygo, and can dip deep into their academy to cover in defence. What they cannot do, though, is figure out how to win when Bellingham is not on the pitch. And with him again suspended for the first leg of their Champions League last-16 tie with Atletico Madrid - this time for accumulation of yellow cards, rather than abusing an official - they simply must snap that streak.

Very rarely are Madrid so outclassed as they were on Saturday.For the second half of the Betis game, Madrid basically stood and watched as Isco pulled the strings for the home side. There was no pressure on the ball, and even an apparent disinterest when their opponents had it. This wasn't a tactical low-block as much as a general ambivalence with absolutely no bite to be found.

That's what they miss when Bellingham isn't there. For some time, the ex-Birmingham City trainee was considered an old-school English midfielder. The Steven Gerrard comparisons were a bit too easy and slightly inaccurate (he's more Zinedine Zidane than Stevie G), but he does have that kind of leadership to him. Bellingham runs, Bellingham shouts, and Bellingham tackles just a little bit too hard while getting away with it. There is a gravitas to the way he goes about the game with the ball, and a real snarl when he's without it.

Madrid don't really have another player like Bellingham in their squad. Luka Modric may wear the armband for Los Blancos, but he isn't really a leader in the same way.

Ancelotti outlined Bellingham's influence in October when he said: "We're satisfied with his work, I'm very satisfied. He works a lot, he's always present, he competes, he fights, he sacrifices himself." Without him, Madrid just look a weaker team.

The defensive numbers back all of that up. Bellingham is in the 92nd percentile for tackles, 94th for interceptions and 91st for blocks, per FBRef. He wins headers, blocks passes and makes clearances at an above average rate.

And so we arrive at the Champions League last 16. The Madrid Derby is always a big occasion, but when Real and Atletico face off in Europe, things go to a new level.

This is the exact kind of contest that Bellingham tends to thrive in, even if his record against Diego Simeone's side is nothing to write home about. He was the subject of hefty criticism for his first two derby showings, and in four Madrid derbies last season, he managed just one assist and no goals. They are, statistically, his least favourite domestic opponent.

But for all of the lack of attacking production, it is these kinds of contests where Bellingham's defensive bite is needed. He relishes a battle like few others in this Madrid side, and if the Betis game was any illustration, the rest of the Real midfield is starting to look a bit leggy without him.

How Madrid address the absence of their inspirational No.5 on Tuesday will be key to the result. Playing the game at the Bernabeu will undoubtedly help - such is the aura of the great stadium on European nights. Still, without their star man driving things in the middle, Real Madrid's signature Champions League voodoo might just be a little bit under threat.