Until the middle of December while under the guidance of Jose Mourinho, Chelsea were often criticised for their style of play as they struggled for results in both the Premier League and Champions League.
However, since the arrival of Hiddink on an interim basis, Chelsea have suffered just one defeat in a dozen matches - which came against Paris Saint-Germain on Tuesday night.
Mikel has flourished since being recalled to the starting line-up under the Dutchman and netted just his sixth goal for Chelsea in the setback in Paris.
The 2-1 loss has left the Stamford Bridge outfit with it all to do in the second leg next month, but the Nigerian international has suggested that he and his teammates remain confident of progressing through to the last eight.
The 28-year-old said to the Mirror: "Guus has come in again and settled the ship. Players feels free to play and free to have responsibility. We thrive on responsibility but do it in a very relaxed way, which is sometimes what players need.
“Guus has come in and done that. We’re picking up results in the league and we’re very much in this Champions League tie.
"We’ve been through a difficult period, no doubt about it, but under Guus we’re picking up results, doing really well back home in the league. This was the first game under Guus in Europe and we’re still very much in the tie."
Chelsea are back in action on Sunday when they host Manchester City in the FA Cup fifth round.