This is a quick healing:
Mark 10:51“What do you want me to do for you?” Jesus asked him.
The blind man said, “Rabbi, I want to see.”
52“Go,” said Jesus, “your faith has healed you.” Immediately he received his sight and followed Jesus along the road.
But then, we have another episode of healing the blind earlier in Mark 8:
22 When they arrived at Bethsaida, some people brought a blind man and begged Jesus to touch him.
The people, presumably his friends, believed in Jesus' power to heal just by touching. This episode of healing started out like the one in Matthew 9:2
Some men brought to him a paralyzed man, lying on a mat. When Jesus saw their faith, he said to the man, "Take heart, son; your sins are forgiven."
But instead of immediate healing,
23 So He took the blind man by the hand and led him out of the village.
There was a long delay. Jesus led the blind man out of the village. Why didn't he do it on the spot?
Then He spit on the man’s eyes and placed His hands on him.
The friends expected just a simple touching on the blind man's eyes, but Jesus spit on the man's eyes first.
“Can you see anything?” He asked.
He asked this wavering question: Can you see anything?! This was a moment of monumental hesitation, dare I say, due to lack of sufficient power?! He didn't need to say that at all in this story and no one would blame him.
24 The man looked up and said, “I can see the people, but they look like trees walking around.”
Apparently, the healing was not quite perfected. It required a second application of dosage.
25 Once again Jesus placed His hands on the man’s eyes, and when he opened them his sight was restored, and he could see everything clearly.
A similar question is asked in In the Gospel of Mark, why does Jesus heal this blind man twice?. The answers brought out some valid spiritual lessons by spiritualizing the episode as a double healing.
I see this as a single healing with a first incomplete attempt. I am not asking what kinds of spiritual or theological lessons can we learn in this episode. I am asking what kinds of spiritual mechanics/dynamics are involved here? Was Jesus tired spiritually? Was Satan there interfering? Was the blind man's faith weak? This episode was unique (or strange) in Jesus' life in terms of the integrity of His power.
Matthew 13:58 And he did not do many miracles there because of their lack of faith.
In Mark, the blind man's friends did have faith and begged Him. Yet, Jesus delayed and was hesitant in healing the blind man.