Bryant made it clear: he specifically wanted Deckard to work on the case.
Bryant: [Holden is] not good enough, not good as you. I need you, Deck. This is a bad one, the worst yet. I need the old Blade Runner, I need your magic.
Quote from this transcript.
However, every single time I watched the movie, what jumped out to me was the fact that Deckard nearly died to every replicants he encountered and only survived because of external factor, sheer luck or circumstances:
- When he got back to his apartment, Rachael managed to sneak into the elevator and went unnoticed until the elevator reached his floor. If she was one of the rogue replicants, she could have easily killed him.
- The first rogue replicant he encountered was Zhora. Because of his (according to many people) bad acting, she guessed he was lying and attacked him when he less expected it. He was about to get strangled to death, but Zhora stopped to run away when people barged into the room.
- The second rogue replicant, Leon, caught him off guard as he was roaming the streets looking for Rachael. Deckard was obviously outmatched and was about to die again... until Rachael somehow landed a headshot with the gun Deckard had dropped.
- The third replicant, Pris, also took him off guard as he was exploring J.F. Sebastian's apartment. She easily dominated him. But instead of finishing him off, she started doing acrobatics (I suppose it suits her personality), which allowed Deckard to land a shot and finish her off.
- The last replicant, Roy Batty, actually injured and cornered Deckard to the point that he was about to fall to his death. But Roy decided to save him for reasons explained in another question.
Considering the fact that Deckard might have ended up just like Holden or dead if it weren't for his amazing luck, what made Bryant believe he was a good Blade Runner?