We know Rangers also receive a speed boost, so it's reasonable to believe that a Morph Ranger's reaction speed is in the ball park of 32 times faster than the average person. Thus, the White Ranger can actually react to attacks in about six milliseconds. To compare, in the same given time, a bullet fired from a gun would've only traveled about nine feet. As the Tigerzord mimics the White Ranger in real-time, it must be capable of the same speeds.
I bet he could totally do that knife finger ...