It's hard to point out Ajax's best player this season. Christian Eriksen is a good prospect, but he's not there yet. They've signed former Liverpool striker Ryan Babel, who was playing at Hoffenheim. What's clear is that Ajax's best line lies on the midfield. Siem de Jong, is the team's goal scorer even though he plays in the attacking midfielder position.
Ajax is having a quite good start to the 2012/2013 Eredivisie, all things considered, and they've only lost against Borussia Dortmund in the first game of the Group Stage after Lewandowski scored in the last ten minutes of the game. Dortmund didn't play that game well, but Ajax's performance surprised most of the analysts that expected to see the German team cruising over Ajax at home.
Again, Ajax should not give Real Madrid a very hard time, but since Mourinho's team considers this match as a "must-win", Frank De Boer and his players could play with Real Madrid's emotions if los blancos don't score early in the game.
As every Dutch team, the defensive line is very bad. Toby Alderweireld is not enough to contain Cristiano Ronaldo, Di María, Benzema or Özil. Vertonghen was an essential player for Ajax, but Tottenham Hotspurs decided to sign him during this transfer window. He even scored in Spurs' last win against Manchester United in Old Trafford.
Sulejmani will likely be their starting striker, and with Babel probably starting on the wing, it will be very important for Real Madrid not to concede easy counterattack opportunities.
Ajax will be a key factor in Real Madrid's group, since they're capable of drawing or even winning a game against Borussia, Manchester City or Real Madrid if these three giants aren't ready for a good battle. But if Klopp, Mancini and Mourinho make sure their team is fully concentrated on the match, neither three should lose points against De Boer and his men.