Right-back: Lukasz Piszczek
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The Polish fullback has been around the Dortmund block for almost a decade now, but his position in the teams remains unquestionable. He's 33 now, but still the managers opt to go with him for most of the important games which actually speaks volumes about the quality of the player.
Piszczek has played only five times out of nine in the Bundesliga but regardless has managed to post incredible figures of 4.4 clearances and three tackles per game average. He started in both the Champions League games too, helping Dortmund to a pair of clean sheets with his defensive nous.
Centre-back: Abou Diallo
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Dortmund's €28 million outlay on an inconspicuous French youngster perhaps fell through the cracks, but Diallo is making sure everyone's taking note of him now. Manager Lucien Favre has started him in every league so far, and the 22-year old has barely put a wrong foot forward. He has anchored the defence with great tenacity, while his ability to sniff out danger has seen him average almost five clearances per game.
What's more, he's got a goal to his name too! Diallo doesn't fear coming raging out of his position and pivot on the attack. His dribbling skills are one of the important facets of his game too, drawing comparisons with those of Eden Hazard. It would be great watching him go against the bullish Costa.
Centre-back: Diego Godin
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With Jose Gimenez sustaining another thigh muscle injury, the onus is on Diego Godin to shut out a high-flying Dortmund attack. And the Uruguayan stalwart is not new to these tasks. He has headlined one of the best defences of Europe's modern football and shows no signs of stopping even at 32. A mortar to Atletico's brick.
Left-back: Lucas Hernandez
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It isn't a name that's normally called out when the talk centres around Atletico Madrid, but Lucas Hernandez is undoubtedly a very important piece of Simeone's jigsaw. At least in the Champions League. He's managed to keep Felipe Luis waiting in the wings in the competition by starting ahead of him in both the games thus far, and is likely to retain his position here too.
The Frenchman possesses excellent passing range and also connects well with the forwards. He doesn't leave much space behind either, tracking back in time to demonstrate great positional awareness too.