Tim Wakefield's (BOS) success as a knuckleball pitcher came from his ability to throw the pitch for a strike. Sunday night's game against the Cubs showed off that ability well.
That's pretty amazing that a pitch with an unknown movement can be so accurate. One reason may be that Wakefield can throw the pitch a bit more predictably than you might imagine:
A high number of these pitches had a nice dip, down, in to left-handed batters, in to right-handed batters. Note that there are many that have no relation to that movement, but that core is the movement on which Tim hits the strike zone. Note that many of the pitches in the zone are high, so with that movement, the ball is falling into the zone, looking like it might be out of the zone at first. Because of that, Tim induced swings at balls above the strike zone, and taken pitches high in the strike zone.
The movement graph also demonstrates that Tim can control the ball fairly well. If he can get a consistent spin on the ball, it should really do the same thing. He's not just tossing it hoping it will find the strike zone. He's replicating the motion well enough that 38 of his 68 knuckleballs ended up in the strike zone, most of those with the movement you see in the concentrated area on the lower chart. That's impressive control of a tough pitch.