Why Sergio Ramos vs. Sergio Aguero Is Key Real Madrid vs. Manchester City Battle

Manchester City’s preparations for the biggest game of their season haven't been ideal. They face Real Madrid on Wednesday in the second leg of their UEFA Champions League semi-final and are well placed to make it to the final.

But unlike the serene preparations ahead of the first leg, where they beat Stoke City 4-0 and rarely got out of third gear, this time they lost 4-2 at Southampton and were run ragged for 90 minutes, hammered in emphatic style.

It was, admittedly, a much-changed side—but City were so abject, it must have worried their fans.

A number of their fringe players were selected to play at St. Mary’s Stadium, an opportunity to play themselves into Manuel Pellegrini’s starting XI in Madrid. Only Kelechi Iheanacho—a 19-year-old with limited experience—made the manager take note, as he scored two in a ruthlessly efficient display.

City travel to the Santiago Bernabeu Stadium having secured a 0-0 draw in the home game last week. It was a decent result. Stopping Real from scoring was perhaps their primary objective, although Zinedine Zidane’s side played so within themselves in the first half, a feeling of regret permeated the Etihad Stadium at full-time. Was it an opportunity missed?

Cristiano Ronaldo has been struggling with a thigh complaint since coming off in the recent win over Rayo Vallecano and missed the first leg. He trained on Tuesday morning and looks set to feature, but City will be hoping he isn’t fully fit. Few players can wield as much influence as he can, particularly in this competition, where his goalscoring record is unrivalled.

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Cristiano Ronaldo training with Real Madrid this morning. pic.twitter.com/ph3DVUbR0f

— Jonathan Smith (@jonnysmiffy) May 3, 2016"

The key for City is whether or not they can score. Sergio Aguero, who was rested at the weekend, is their principal goalscorer. Do their hopes of progressing to the final in Milan rest on the Argentinian’s shoulders?

His battle with Sergio Ramos is likely to be crucial. Despite his disciplinary issues, the Spain international is one of the finest defenders in the world. He reads the game superbly well, is good in the air, comfortable in possession and a goal threat from set pieces.

If a striker wants to try to play a technical game, Ramos is equipped to deal with them, and if it turns physical, he can more than handle himself. He thrives on adapting his game to whichever opponent he is up against.

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Our record at home in the @ChampionsLeague this season: 18 goals scored, none conceded!

🎥 https://t.co/G1sDRQwq2G pic.twitter.com/Enx4pX0My6

— Real Madrid C.F. (@realmadriden) May 3, 2016"

It is telling that Atletico Madrid manager Diego Simeone claimed earlier this season that he would love to see Ramos in his side. "I admire and respect him,” he said, per Marca. “And if I could choose players from outside of my group, he would be the one that I would take.”

But perhaps the most glowing endorsement came from his former boss Carlo Ancelotti, who described him as a “complete” defender.

Per World Soccer Talk, Ancelotti said:

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It’s difficult to compare him to other players. 

There are defenders with technical quality, others with defensive qualities, and others who stand out in their ability to mark, like Cannavaro. Others, like Baresi, controlled the defensive line very well.

Ramos, if I had to place a quality on him, is the most complete. He has a bit of everything. Personality, skill, he manages the line well. He might be the most complete defender I’ve seen.

"

Shaun Botterill/Getty Images

But Aguero has looked sharp this season, particularly since the turn of the year, when he put his injury problems behind him and played a run of matches problem-free.

The Argentina international has scored 28 in all competitions and looked at his best for much of the campaign. Quick, sharp, strong and lethal in the box—he’s the best in the English top flight.

In the Premier League alone, he’s scored an average of 0.82 goals per game—an increase on the 0.79 he managed last season. He’s looked supremely focused whenever he’s been given an opportunity to score.

Only Thierry Henry can match Aguero for efficiency in Premier League history, with 0.62 goals per game. It’s a remarkable record, and with the City striker still just 27, it’s arguable his best years are ahead of him.

Shaun Botterill/Getty Images

Ramos must be put under pressure. Like many defenders, he looks most vulnerable when a striker is running at him. Aguero, fearless in possession and so quick over the first five yards, can unsettle even the world’s best.

The big question for City ahead of the game is whether Iheanacho has done enough to claim a place alongside Aguero for the game against Real, or whether Pellegrini will go with the safer three-man midfield option, with Fernando, Fernandinho and Yaya Toure operating in tandem.

Iheanacho has looked ready for regular first-team football almost every time he’s been given an opportunity this season, scoring 13 in all competitions at a rate of a goal every 79 minutes he’s been on the field. For a 19-year-old being used intermittently, it’s a fine record.

BEN STANSALL/Getty Images

His cameo display in the first leg against Real saw him struggle to impact the game—but his clinical display against Southampton only further underlined what we already know. Iheanacho is a special player, and special players impact the biggest games.

If he did start, it would give Ramos and Pepe an additional problem, but it would also leave City open to counter-attacks, something they have fallen foul of in Europe before. Real, perhaps the best counter-attacking side in world football, would likely punish a City side short of numbers in midfield.

Whichever formation Pellegrini opts for, the performance of his main striker is going to be hugely important. He’s up against one of the greatest defenders of all time, but he is capable of having a significant impact.

Rob Pollard is Bleacher Report's lead Manchester City correspondent and will be following the club from a Manchester base throughout the 2015/16 season. All quotes were obtained firsthand unless otherwise noted. Follow him on Twitter @RobPollard.