Who should replace Marcelo against Atlético de Madrid?

* The Thought Experiment series will explore ideas that are highly unlikely to happen, but are interesting to think about. If you have an idea for The Thought Experiment Series, please email them along with your name and location to mustafajangRM@gmail.com *

Following Marcelo's phantom foul on Torres, referee Milorad Mazic decided that breathing on Fernando warranted a yellow card, leaving Ancelotti without his first choice left-back. Nicholas Rigg wrote about Coentrao's probable placement into the starting 11 to replace the Brazilian. While Coentrao is the obvious choice to step in, his form of late has left much to be desired.

As Nicholas mentions, in a game where most every player looked poor, it was Coentrao who had arguably the worst game of all in Real's 0-4 thumping in the Calderon a little over two months ago. So who are the alternatives to the Portuguese international?

Option 1- Gareth Bale to left back.

This idea has become more and more popular in the media in the past few days, with a Marca poll stating that over half of Real Madrid fans that voted want Bale to replace Marcelo at left-back. Of course, the Welshman started his career at the position while at Southampton, and was impressive in the role to be sure. However, that form seemed to elude Bale after his transfer to Tottenham, and it wasn't until he was moved to the midfield that he began his rise to stardom. Bale at left-back would allow Ancelotti to put Isco back into the starting 11 (forgetting for a moment recent reports that Isco and Ancelotti have had disputes about the attitude of the young Andalusian). Bale would definitely help replace the marauding runs of Marcelo and might provide some space for Benzema and Cristiano to work if Ancelotti moves to a 4-4-2.

The negatives of this move are clear. Bale hasn't show the pension for playing much defense recently and I am not sure how he and Ronaldo would work together on the left side. Marcelo and Cristiano have formed a wonderful partnership sharing the left flank and seem to work brilliantly off each other. This crucial link would be missing if Bale was slotted in at left-back.

Option 2- Play all 3 CBs and Carvajal, with either Varane or Ramos at fullback

This option is even crazier than the first, but it's still an interesting one to consider. I'll be the first to admit I was worried about Varane in the starting lineup on Tuesday, as his last encounter with Atletico didn't go so well. To his credit, he was brilliant, save a few mental mistakes. He won the majority of the aerial balls sent his way, and was generally very solid in the back. What caught my eye, however, was his effort to push forward.

Obviously, this particular run comes from the right side, and asking him to switch sides to the left is a huge request, but an interesting proposition. I personally love the idea of having Varane in alongside Pepe and Ramos, as his pace and ability to win aerial battles is crucial against a team such as Atletico, who are so dangerous from set pieces.

Similarly, Carlo can opt to move Sergio Ramos, who has a pension for getting forward anyway, to his original role of full-back. Ramos has gone on record as saying he doesn't want to play full-back, so this is pretty unlikely as well, but he has shown he has the skill set for it. Ultimately, I think that Carlo would be hesitant to break up the Pepe-Ramos partnership.

Fabio Coentrao will no doubt be the starting left-back when the team returns home to the Bernabeu, but it's always fun to think about interesting lineups that Carlo can throw out there. How would you replace Marcelo?