Funny because that split-second makes a difference. I was sparring a Mayweather carbon-copy, so I threw a jab and returned it low, knowing he'd throw his own jab; I slipped right to come back with a right over the top, but by then it was just too late and he rolled with it. I wasn't so mad that it didn't work, but I was mad I had wasted a counter. He wasn't going to fall for it again, at least not anytime soon. I probably made him miss by too wide a margin and slowed my return. Maybe slipping inwards and landing a right over the top would have worked, provided I was low enough to evade his straight right.
Should have slipped in and hit his body; he cannot hit you with his right while his left his out. Or slip outside and hook his body with your left, or a right uppercut to his ribs.
Pressure - Swarm him and never give him time to counter or force him to counter when uncomfortable. This is a lot harder than it sounds because the footwork required to keep a counter puncher trapped and or backing up is seriously underrated. Especially since counter punchers are usually among some of the most gifted athletes as far as speed, quickness, and fluidity. Duran, Margarito, Williams, Froch/Dirrell etc... are good examples. Power - It is Boxing. People get hit. With the right amount of power? A power puncher can catch and end a Counter Puncher. This requires serious mental fortitude, focus, and patience. It is likely that a Puncher will be losing the entire fight. He needs to believe in his power and NEVER hesitate when an opportunity presents itself. Many times, Punchers get trigger shy or locked into one punch. Randal Baily, Shane Mosely, etc... are good examples. Timing - Counter Punchers are usually fast, but timing beats speed. This requires a very high ring IQ because it will take understanding of the opponent and setting traps. If you can create situations where you are still in position to punch after throwing out something too sweet to not to bite on? Great. Kostya Tzyu/Judah and Marquez are good examples. Counter Punching - This is extremely difficult and usually only works when one Counter Puncher is many levels above the other. Counter Punchers by nature don't bite on feints and only engage when it is completely to their advantage (or forced to). Zab Judah (rds 1-4 vs FMJ), Mayweather/Marquez is a good example. In the hands of the superior athlete Counter Punching is probably the Sweet Science personified, but that is the beauty of Mastering the Sweet Science... There is always a way.
If you see an opening like that it may be worth it to let him connect once. I have done this with certain shots I know I can not be hurt by. Let a lazy jab land once or twice so the guy is confident in it and not just "testing" and defensively 100%. Counter Punchers test a LOT. Seems like sparring is the worst place to face a counter puncher because you don't get to wear him down. IMHO, when facing a CP a person should just write the first few rounds off and just focus on making the guy punch more than he wants to and body work.
That's one of the best counters for a jab: lean back a little but still let the jab hit you, then rock back over top with a right. Duran was a beast at that.