Chelsea defender Aaron Anselmino has joined Borussia Dortmund on a season-long loan deal.

The 20-year-old will wear the number 28 shirt at Signal Iduna Park, where he could make his debut against Union Berlin on Sunday.

Anselmino signed for the Blues from Boca Juniors last August, but spent the first half of last season back on loan with the Argentine giants.

The centre-half made his Chelsea debut as a late substitute during their 4-1 victory over Benfica in the last 16 of this year's FIFA Club World Cup.

Anselmino's move comes after Enzo Maresca encouraged him to gain experience elsewhere, while Dortmund are also facing something of a defensive crisis.

"I'm very happy about this step," Anselmino told Dortmund's official website. 

"I've been told a lot of good things about the BVB fans and about the size of the club. I'm therefore very happy and am really looking forward to it."

"Due to the injuries to Emre Can, Nico Schlotterbeck, and Niklas Sule, we were forced to make adjustments at centre-back," Dortmund CEO Lars Ricken explained.

"Aaron has already gained first-league experience in his home country and has great potential. It was no coincidence that Chelsea signed him to an extremely long-term contract last summer."

Anselmino is Dortmund's fifth signing of the current transfer window - and second from Chelsea in as many days, after Carney Chukwuemeka signed a five-year deal at Signal Iduna Park on Tuesday.

As for the Blues, who are also reportedly looking to offload the likes of Nicolas Jackson, Christopher Nkunku, Raheem Sterling and Ben Chilwell, they have now used five of their six available international loan spots.