The winter transfer window typically serves much more to cover team deficiencies in certain positions than to strengthen with a big-name signing. And Chelsea, hit by injuries, especially in its defensive line, has moved quickly.

To the already known long-term absence of Levi Colwill are added the recurring physical problems of Wesley Fofana and Benoit Badiashile, leaving Trevoh Chalobah as the only 'blue' center-back in perfect condition so far this season.

After attempting the signing of French Rennes center-back Jeremy Jacquet, for whom the Ligue 1 club was asking around 70 million euros, Chelsea has moved its pieces to fish in Germany.

And it has done so at Borussia Dortmund, the team to which it had loaned one of its numerous gems at the start of the season.

This is 20-year-old Argentine center-back Aaron Anselmino, who, while it's true he began the season with very little playing time, in recent months has become a regular in the heart of the defense.

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His high level, both in playing the ball out and in defensive actions, has led Chelsea to recall him from his loan so he can join Liam Rosenior's squad immediately. Great news for the English manager of the Blues, who will have greater squad depth and at his disposal a center-back with a very bright future.

In short, for Borussia Dortmund, it is very bad news because the defensive squad is weakened. With the injury to Niklas Sule and the expiration of his contract at the end of the season, the club now has only three center-backs available for the three-defender formation used by manager Nico Kovac.

This situation reduces options for competing in the Bundesliga, where the team is looking to challenge Bayern Munich for the title.

From Chelsea's side, the decision is justified by the need to strengthen the defense after analyzing the options available in the transfer market. The London executives chose to recall Anselmino instead of activating the buy-back clause for Mamadou Sarr, who has just returned after winning the Africa Cup of Nations with Strasbourg.

While the Argentine returns to London to integrate into training and compete for a spot, reports suggest he may not have a starring role for the remainder of the season, according to English media. The decision for his return, however, was described as "decisive" by Chelsea's leadership, who see him as a key piece for the sporting project.

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