The healing story in 8:22-26 is one of the major hinges of the Gospel of Mark and serves to bridge the first section of the book with the middle section. Another healing of a blind man - the beggar Bartimaeus - will serve as the other major hinge into the third and final section of the Gospel.
In the first section of Mark, Jesus is revealed as the Messiah in power. He performs many healings, drives out demons, and demonstrates his power over nature. Woven into this section are three boat stories and three bread stories. The boat theme in the calming of the storm and walking on water along with the bread theme in the feeding of the 5000 and the feeding of the 4000 find their common culmination in the story leading right up to ours, which I'll return to in a moment.
In the second section, though, the Messiah is revealed in weakness. Jesus begins to teach the disciples that the Messiah must suffer, be rejected, and die. Three times he tells his disciples this and three times he corrects their misapprehension of his purpose.
To return now to the third bread/boat story, we find Jesus warning the disciples about the yeast of the Pharisees, the disciples failing to understand him and worrying that they have not brought bread, and Jesus rebuking them by reminding them of the feedings and asking, "Do you still not understand?"
Immediately following our healing story, Jesus asks the disciples the key question of the Gospel: "Who do you say I am?" In one sense we see that Peter has begun to understand, but in the immediately following story Peter shows he does not yet fully understand, being rebuked by Jesus for his protestation of Jesus' pronouncement about his coming death.
Finally we're in the place to see why Mark places the healing story between the rebuke on the boat and the rebuke in Caesarea Philippi. The healing serves as a parable or metaphor of sorts to the condition of the disciples. The question from the previous section - "Do you still not understand?" - begins to find a positive answer. This is reflected in the first stage of the healing. Just as the blind man begins to see but not quite right, so also the disciples have begun to understand about Jesus as the Messiah, but they do not yet understand quite right because they do not yet grasp that the Messiah must suffer and die.