Arsenal have been linked with signing goalkeeper Loris Karius, a move which would place doubt over the future of Wojciech Szczesny.
Karius is already established in the first team, and is seen as a natural competitor for Manuel Neuer at international level, currently part of the under-21 side.
Most intriguingly of all, his contract runs out in June, which would allow Arsenal to begin negotiations over a free transfer already.
Karius used to be part of Manchester City's youth set up before leaving in 2011 without playing a first team game.
He told ClubSGP last year in an interview: "Unfortunately I broke my hand in training in November 2011, which required surgery, and because City were in the Champions League, they needed three keepers so they brought another goalkeeper in.
"That left me further down the pecking order, and as I was getting to the age where I needed to think about first-team football, I joined Mainz, back home in Germany."
With David Ospina and Emiliano Martinez at the club, Arsenal signing Karius would add to a congested goalkeeping selection pool.
Szczesny's position as number one goalkeeper would be under further threat, and based on his performance against Southampton alone, it's an area which requires improvement.