Jose Mourinho is sure that he will have a big role to play this season, telling Sky Sports:
I think we need him. We need him as a player for our squad to be the way I like. I like my squad with different qualities, not just as football players but also in terms of personalities. I like to have players with different personalities.So as a player and person, Didier is somebody we need to be strong.
However, his strength has already been called into question after he limped off against Ferencvaros in pre-season, per The Guardian. Having recovered quicker than many expected from this minor injury, maintaining his fitness will be crucial to his involvement in the 2014-15 campaign.
Although Costa will be the first-choice front man in all competitions, Fernando Torres' continuing failures will make Drogba the back-up striker. If Costa is injured, Chelsea will need Drogba to return in the same form as he left the club two years ago.
After he re-signed for the club, Drogba told the official website:
I think the best thing I can bring to this club and team will be to stay the same as I was during my first spell here. I don’t have to change, everybody knows my character, my attitude and my mentality. They know if I’m here it’s not just to smile and thank people for welcoming me back. I want to win, I want to share my desire and will to win games.
While he obviously believes that he can achieve this—he wouldn't have returned otherwise—it is doubtful that the Blues will be able to rely on him on a regular basis this season.
Drogba's legendary status at Stamford Bridge was not cemented by being the most prolific striker. He only bagged the top-scorer prize in two of his eight seasons at the club and was outscored by John Terry in 2011-12.
However, despite his age and the ailments that come along with it, he still presents a better back-up than Torres. The element that makes Drogba preferable as a deputy is the timing of his goals.
He holds the club record for Champions League goals with 34 strikes to his name, and he has scored eight times at Wembley. Every domestic cup final that the Blues featured in had a goal from him to see them on their way.
The penalty that won the Champions League in Munich only added to the last-minute precision header that got Chelsea that far in the first place and rounded up the number of trophies he won with the club to an even 10, per Dan Ripley at the Daily Mail.
Torres has also found some success on the biggest stages. His goal against Barcelona in the 2012 Champions League semi-final will live long in the memories of supporters, and he scored the opening strike in the 2013 Europa League final.
However, he has consistently struggled against teams that Drogba used to routinely pick apart.
As things stand at the moment, Chelsea appear to be hanging all of their hopes on keeping Costa fit through the whole season.
At 36 years old, Drogba is not going to be able to have the same impact as he had in his first spell, and expecting otherwise will only set him up to fail. While he will make for a great super-sub, especially in big games, the Blues will come unstuck if they are forced to rely on him to lead the line on a regular basis.