The Ivorian striker returned to the club he left in 2012 earlier this summer after stints with Chinese outfit Shanghai Shenhua and Galatasaray.
Drogba scored 157 Chelsea goals in an eight-year period from 2004-2012, and he departed for China with three Premier League titles, four FA Cups, two League Cups and a Champions League win in his medal haul.
The Blues legend returned on a one-year deal this summer, and while new £32million signing Diego Costa is likely to be first choice at Stamford Bridge, Drogba will provide the Spain international with some stiff competition for a place, alongside Fernando Torres.
And Nigerian midfielder Mikel, who played with Drogba for six years, thinks that Mourinho was instrumental on his teammate's comeback.
He told the club's official website: "I heard the rumours [about Didier's return] but I thought there was no way it was going to happen. I thought when he’s gone, he’s gone. But then I thought about it a bit more and I realised it could happen because of the connection that the gaffer and Didier have always had.
"I’m glad to have him back. It’s like his home. He’s fitting in perfectly well again. It’s like he never went away. It’s good for the team because he’s a big player and a big personality."
Mikel also explained how Drogba's talents and accomplishments see him command instant respect from all concerned with the club, while he also lamented the departures of Frank Lampard and Ashley Cole - two players who were fundamental to much the side's success over the last decade.
"It’s a shame we lost Frank and Ash - two big personalities and two big players," he added. "But Didier is back. I think we need a bit of his personality and his physicality in the Premier League, too. He can offer that.
"He stills gets respect from everybody in the dressing room: the older guys, the younger players, everybody. We are all glad to have him back.
"Hopefully it will be a very successful one for the team. Everyone wants to achieve something. We want to win trophies. We didn’t do that last season but this season we are all hoping we can have a good season and win some trophies."
It has been a busy summer so far for the Stamford Bridge side. Costa has arrived alongside former Atletico Madrid teammate Filipe Luis, while Barcelona star Cesc Fabregas risked the wrath of Arsenal fans after joining for around £30million.
Meanwhile Cole joined Roma on a free as Lampard left following the expiration of his contract after David Luiz had agreed to join Paris Saint-Germain.