The Columbus Crew centre-back picked the Arsenal midfielder over Manchester United’s Casemiro and Manchester City’s Rodri.
Mensah was reacting to a post made by TV3 Sports’ Juliet Bawuah, who had asked her followers to pick who the best was among the trio.
The 32-year-old made his pick in the comments section, writing “T for Thomas [Partey]” accompanied by some emojis.
Partey is currently playing his best football since joining Arsenal and has two goals to his name in the ongoing campaign.
The Ghanaian has been an integral part of Mikel Arteta’s side, as they sit five points clear at the top of the Premier League table.
Meanwhile, Arsenal legend Ian Wright believes the Gunners have a good chance of winning the Premier League if their key players, including Partey, stay fit.
The former England forward named Partey, Bukayo Saka and Martin Odegaard as the club’s most important players at the moment.
Arsenal have surprised everyone this season with their impressive form, having lost just one game in the league thus far – a defeat that came against Manchester United.
“But when you look at the team this season, Saka's done it, Partey's done it, Odegaard has done it.
“Those are the ones, if Partey, Odegaard and Saka stay fit – which is going to be very tough – then I think Arsenal have got a very good chance of winning the league,” Wright said.