The Ivory Coast international was a notable absentee for last Sunday's Community Shield clash against rivals Manchester United at Wembley.
"It's better to have injuries now than in the middle of the season or at the end of the season when everything is crucial," said Mourinho.
"If everything goes well we'll have a better situation than last week. I hope [Saturday] I won't lose three players, like I lost the day before the Community Shield game.
"If everything is normal on Saturday I'll have around 19 to 20 players to make a choice of 16.
"Ballack and Bridge they are out of the picture, because we are speaking about surgeries.
"I can't set a date when they can be back. The only one else out of the game is John Terry.
"Maybe I could say Drogba is out on Sunday and he plays, so I don't want you to say I'm hiding something."