Lince had placed a great deal of Qi into his dagger when he decided to throw it this time. He had already let one dagger go and lost it during his fight against Red, which had been a considerable setback.
Throwing another one again presented quite the risk, but he believed that the element of surprise would be on his side this time. He felt that the suddenness of the attack could catch his target off guard, allowing him to turn the tide of the battle, even if only momentarily.
After all, even when he had thrown the dagger against Red before, it had still been effective in striking its target.
The problem was that it simply did not achieve the outcome he had originally intended. The dagger had not inflicted the level of damage that Lince had hoped for.