William Saliba’s lengthy injury lay-off could force Mikel Arteta to begin Arsenal’s Premier League title defence with a new centre-back partnership, and Sunday’s meeting with Borussia Dortmund offers a crucial first test.
Saliba is facing an extended period on the sidelines while Arsenal manage the back problem which affected him during the World Cup.
The Frenchman has been central to Arteta’s defence for several seasons, but Arsenal cannot afford to wait for his return before finding an alternative.
That places greater responsibility on Cristhian Mosquera.
ReadArsenal’s latest Borussia Dortmund preview outlines Arsenal’s defensive injury problems, with Jurriën Timber also short of fitness ahead of the new campaign.
Gabriel Magalhães is back, however, and Sunday could offer a first proper glimpse of Arsenal’s new-look centre-back pairing.
🚨🔴⚪️ BREAKING: William Saliba will be out for extended period but NO surgery.
“Extensive assessments have concluded that surgery is not recommended, but William should now commence a managed recovery programme”.
•William’s rehabilitation will commence immediately, with… pic.twitter.com/4FgLqQOQZI
— Fabrizio Romano (@FabrizioRomano) July 22, 2026
William Saliba injury opens door for Cristhian Mosquera
If that happens, Arteta will be watching far more than another pre-season partnership.
It could be the pairing he needs when Arsenal begin their Premier League campaign.
Mosquera was originally signed from Valencia for around £13million in 2025 to provide competition and cover for Saliba and Gabriel.
He has since become considerably more established.
The 22-year-old made 25 appearances by March of his first Arsenal season and earned a maiden senior Spain call-up, demonstrating how quickly he adapted to English football.
Mosquera has also previously spoken about the influence Saliba and Gabriel had on helping him settle in north London.
Now he could be required to replace one of them.
ReadArsenal reported on Friday that Gabriel had returned to Arteta’s squad ahead of the Dortmund game, giving the manager at least one established member of his usual partnership back.
Mikel Arteta needs answer before Premier League opener
Saliba’s situation makes the remaining pre-season games much more important.
The Standard reported when Arsenal confirmed the injury that the club expect him to be unavailable for an extended period as he undergoes rehabilitation.
Surgery has not been required, but there is no reason for Arsenal to take risks with one of their most important players.
That leaves Arteta needing a dependable alternative immediately.
Mosquera possesses many of the attributes required.
He is quick enough to defend large spaces, comfortable receiving possession under pressure and already understands the aggressive defensive line Arsenal prefer to use.
Playing alongside Gabriel should also help.
The Brazilian provides experience, physicality and leadership, allowing Mosquera to concentrate on adapting to the increased responsibility rather than becoming the senior figure himself.
Dortmund should provide a serious examination.
Arsenal’s defensive line will be tested against Champions League-level opposition, giving Arteta a useful indication of whether Gabriel and Mosquera are ready to begin competitive football together.
Saliba remains the first choice once fit.
Until then, Arsenal need someone else to make his absence hurt as little as possible.
Mosquera was signed as depth. Saliba’s injury may now give him the opportunity to become much more than that.
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