The centurion had power, position and money. In fact, even though he admits he is still under authority, he could have easily been prideful and arrogant, considering his status.
However, the centurion had compassion and love. He did not view his servant as an 'object' to serve himself; but rather a human being in pain, or 'terrible suffering'.
The centurion humbly sought Jesus himself, instead of sending another servant. Not only that, but he recognized that he was nothing before Jesus, he had done nothing to deserve Jesus to come to his house.
More so, the centurion had faith, he had belief. "Just say the word, and my servant will be healed". He did not make any wishy-washy pleas or doubtful requests. He was certain and convinced.
He even describes some of his (human) authority and how his word is final and true. But how much great is the authority of Jesus, who has heavenly authority - all Jesus had to do was command and it was done.
"When Jesus heard this, he was astonished"... I kept asking myself, how is Jesus astonished? Jesus knew what was to come, he knew of the Pharisees's conniving and of Judas's betrayal. He knew what cup the Father had given him. Why was Jesus surprised by this man's faith? Surely he knew what was going to happen. I understand why Jesus wept - he is compassionate and loving, but surprise con notates unexpected.
I decided to go back to my definition of astonished. The word used is 'thaumazó': wonder, admire, marvel. Wonder is "a feeling of surprise mingled with admiration, caused by something beautiful, unexpected, unfamiliar, or inexplicable."
"I tell you the truth, I have not found anyone in Israel with such great faith. I say to you that many will come from the east and the west, and will take their places at the feast with Abraham, Isaac and Jacob in the kingdom of heaven. But the subjects of the kingdom will be thrown outside, into the darkness, where there will be weeping and gnashing of teeth."
"Jesus said to the centurion, "Go! It will be done just as you believed it would."
(Good blogpost here: http://www.jenniferblairblog.com/2013/04/22/the-motivation/)