Paul Merson has described Thomas Partey as the “number one” signing of the summer, and expressed shock that Arsenal were able to land the midfielder from Atletico Madrid.

Partey made the move to north London from the Spanish capital on the final day of the summer transfer window.

The early signs have been positive, with the Ghana international impressive in Arsenal’s 1-0 win at Manchester United on Sunday.

Merson was not blown away by Arsenal’s performance at Old Trafford, but Partey caught the Gunners legend’s eye.

“It was a good away performance. It wasn't great - I wouldn't get carried away and say, 'Oh my god it's a turning point',” Merson said on Sky Sports.

“They beat a terribly, terribly poor Manchester United team on the day. They've done a job, we've seen them lose those games over the last five or six years. But I think Partey's a massive, massive difference. I mean, what a signing.

“When you talk about signings in the summer, he's got to be number one. I cannot believe, without being horrible here, that Arsenal got him. I don't mean that in a horrible way, they're all crying out for it - I know Manchester United are top-heavy and they've got Fred, McTominay and Matic, but they haven't got a Partey.

“Manchester City, too. Fernandinho's coming towards the end, Rodri hasn't really pulled up any trees. You're thinking, 'Wow, who didn't see this?'”

Mesut Ozil, meanwhile, has been catching the eye with his social-media game, as opposed to his on-field displays. The 32-year-old has not featured for Arsenal since their 1-0 win over West Ham in March, but Merson feels there is a route back into the side for Ozil – due to the presence of Partey.

“I think there's a stage for Ozil now that Partey's in the team,” Merson said. “I watched Chelsea play against Burnley, they played N'Golo Kante in front of the back four and let everyone else get on with it.

“They ripped Burnley to shreds, I haven't seen too many teams make Burnley look bang average. Because Kante was playing in that holding role, it gave Kai Havertz and Mason Mount the freedom to do what they want, they didn't have to spend most of their time on the edge of their own box tracking back.

“With Partey in there now, who's so dominant in there and doesn't lose the ball, I think there's a place for Ozil now.

“Then if they do drop someone in to pick up Ozil, you've got someone like Partey who's very comfortable on the ball and can hurt you. Then that frees a midfield player up. I think there's a trick being missed here, but that's just me.”

Ozil has not been included in Arsenal’s Premier League or Europa League squads, so the only route into Mikel Arteta’s team until the registration window reopens in January is via the Carabao Cup.

Arsenal face Manchester City in the quarter finals of the Carabao Cup in December.