Arsenal's search for Per Mertesacker's long-term replacement is finally at an end.
According to Sky Sports Germany reporter Marc Behrenbeck (see below), the 24-year-old has signed a five-year deal at the Emirates Stadium and will be announced on Tuesday.
Paperwork is all that's left to be completed.
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And what a coup Mustafi represents for Arsenal, even if he will set them back somewhere in the region of £35 million.
Young, commanding and experienced at European and international level, the German World Cup winner has all the attributes to thrive in the Premier League, especially so alongside Laurent Koscielny.
But why Arsenal? What convinced Mustafi to up sticks in La Liga and join Arsene Wenger in north London?
Well, in an interview with Sky Germany - which aired earlier this afternoon - he revealed just that (quotes translated by @afcstuff).
He said: "[Arsenal are] a big club - a giant club - with giant history, a club that always plays up there, always in Europe too.
"I've taken a step forward, that was important to me. In my career, I've always looked out for taking steps forward.
"Playing in the Champions League and with teammates who I can learn from, who have big experience, so that's why I moved there."
Wenger and Ozil's presence at the Emirates Stadium also played an important role.
"For me, it's important to have a coach who has been there for many, many years and takes care of everything," he added.
"I haven't spoken to Per [Mertesacker] yet, but I spoke with Mesut [Ozil] and he told me everything [about the club].
"[He said] how the club is and how it's run. Everything he said was very positive and I was quickly convinced."
By signing the Germany international, Arsenal have not only solved their defensive crisis but also improved the quality of their back four considerably.
The Gunners' defence will now read as follows: Hector Bellerin, Koscielny, Mustafi, Nacho Monreal.
Is it a defensive line worthy of winning the Premier League? Who knows, but with the arrivals of Granit Xhaka and Lucas Perez from Deportivo La Coruna, Wenger has a stronger squad at his disposal and one that will allow rotation.