Drogba played alongside Salah and De Bruyne early in their careers, with both players leaving Stamford Bridge due to a lack of playing time.
"When you see those two players, you are very happy to see the way they improved and became leaders in their own teams," Drogba told Goal at Geneva Motorshow - courtesy of Yokohama Tires.
"Mo, I am really happy for him. It is going to be an interesting title race, really interesting. They are two different times. Mo wasn't playing much. Now they compare to the guy six or five years later, who has improved and he is playing games every weekend, every game.
"So, of course, he is going to score goals. The guy is talented, we saw that in Chelsea, so I am not surprised. We saw it in training, but it was difficult. We had Eden Hazard. You have [other guys]. There was a lot of competition for places. That's football also.
"Credit to him, when he left he proved to everyone that he is a great player. That's what I like about him. He left, he didn't succeed at Chelsea. He went to Italy, to play, get some more minutes, comes back to the Premier League and now he is killing it.
"I think for Kevin, the same thing. He was really young, and in the team, we had all these big names. He decided to go and play. In football, it is straightforward, the more you play, the better you become. The more you can understand the game, the more you can read the game and become confident.
"That's exactly what happened with him. When you have a manager like Guardiola who is helping him to understand and read the game faster, wow, he has become a different player. I don't know, but it is going to be very interesting. I am going to follow it to the end. There will be more things happening for sure."