Essien and Mikel played together at Chelsea for many years and were part of the group that made the Blues a successful side in England and in Europe.
The duo were both signed by Jose Mourinho and went on to win multiple Premier League titles as well as the UEFA Champions League with Chelsea.
Speaking about his former midfield partner, Mikel said Essien was a monster in training and described him as a powerful machine.
“He [Essien] never gets the credit that he deserves. We call him the train in training. He is a powerful machine, the way he trains. Every day he’s there working and working,” the ex-Nigeria captain told Dubai Eye.
“Apart from football, what a gentleman he is. He is the train, he is the bison and that’s what we call him.”
Essien enjoyed a trophy-laden career which lasted over a decade and a half following his breakout year at Lyon, where he won two Ligue 1 titles.
He became Chelsea’s record signing when the club forked out £24.4 million to price him away from Lyon in 2005.
He spent almost a decade at Stamford Bridge, helping the Blues to win two Premier League and FA Cup titles, four FA Cups and the UEFA Champions League in 2012.
The 40-year-old also had stints with Real Madrid and AC Milan before calling time on his career after a brief spell with Azerbaijani side Sabail FK.
Essien has since taken to management and is currently serving as a first-team assistant coach at Danish side FC Nordsjaelland.
He also recently acquired both the UEFA A and UEFA Elite Youth A licenses.