Partey started in defensive midfield for the Gunners as they were held to a goalless draw by Villarreal on Thursday night, which saw them knocked out of the Europa League.
“We thought we were signing the next Patrick Vieira, and he hasn't looked like that at all," Keown told BT Sport.
“He started with an injury, he came back early and then got injured again. He doesn't seem to have the legs in midfield, certainly on his own."
Wilshere spent 10 years in Arsenal's senior squad and has disagreed with Keown's assessment of Partey's abilities.
“They're good players. Thomas Partey is a top, top player," the 29-year-old told talkSPORT.
“I played against him in the semi-final of the Europa League and he was one of the toughest I played against.
“The recruitment is not down to Arteta. He's the coach, he's the manager and he picks the team.
“It is down to him to get the best out of them, but I wouldn't say the recruitment is down to him anymore."