Despite the loss, Keown, the former Gunners defender, was impressed with Colombian duo Carlos Cuesta and Jhon Lucumi during their Champions League defeat in Belgium.
Keown told BT Sport: “(Cuesta) looks some player by the way, both Colombian central defenders look pretty decent.
“If I was an Arsenal scout – and never have been, never been asked to comment ever as a former player on prospective purchases – these two are not bad, I can tell you.”
Arsenal are also reportedly weighing up a swoop for Red Bull Leipzig defender Dayot Upamecano in January, after their summer bid of £40million was rejected, with the Bundesliga side holding out for a fee closer to his £82million release clause.
Arsenal instead landed David Luiz from Chelsea on Transfer Deadline Day but will be looking to add further depth to their defence.