"He also has had slightly more success against lefties than he has against righties registering an OPS of .683 to .743 respectively against each."
A few more commas, if you please, sir.
I would put a comma after "righties" and ".743". I would also drop the "against each" and change "to" to "and".
"He also has had slightly more success against lefties than he has against righties, registering an OPS of .683 and .743, respectively."