Partey was a surprise absentee from Ghana's latest squad and his national team's Football Association released a statement claiming Arsenal had told them the midfielder would be sidelined "for a while” after suffering an unspecified injury in training.
The Gunners were quiet on the subject on Saturday when the news broke but on Sunday, ahead of the huge Emirates Stadium clash, confirmed the news in a short statement.
The tweet read: “Thomas Partey is absent from the squad due to a groin injury.”
Speaking after the game, Arteta admitted to fears over how long the midfielder will be sidelined.
“It doesn’t look good,” Arteta said. “I believe he’ll be out for weeks. I think it’s more a groin [than a hamstring problem], but it could be something in between both.”
It is the eighth injury Partey has suffered over three years at Arsenal, but the first in 11 months after two spells on the sidelines at the beginning of last season.
The 30-year-old has now missed a total of 45 games missed for both the Gunners and Ghana.