Manny will just time Spence ducking and after coming up, Manny will close the distance while Spence is ducking then starting to raise up, Manny will fire his one two, one two, then his hook, Spence will get buzzed and smile, this will keep happening until Spence stops ducking, if he doesn't stop coming in throwing his jab combo then ducking slipping out while raising up, Pac will continue to make him pay busting him up, maybe even getting a knockdown.
Spence needs to keep Manny at a distance using his jab as a range finder then slip on the inside, when he's done firing combos instead of dipping down, then raising up, he needs to skip back using quick footwork with his body up chin tucked in, then fire hard power jabs to keep Manny from trying to land counters trying to close the distance, something Floyd did regularly, fire combos then skip back quickly, then back to his jab.
The angle is on Spence left side, what Manny was doing against Diaz, Manny would counter with his right hook, stepping to David's left side circling Diaz, but can Manny get past Spence jab ? because he has the reach, Manny would have to get on the inside after slipping Spence jab, then throw his hook after his combos sliding on Spence left side, then firing combos after Spence steps over following Spence firing combos until Spence backs out or holdd or Manny gets fatigued, Manny can also land his body punches at that angle Spence left side and to the middle solar plexus, then turn Spence while he's covered up, something he's been doing in sparring, Spence has been getting counted and then covering up because he doesn't know were his opponent is, so his natural reaction is the shell up, with his head tucked in, if he constantly does this he will lose close rounds giving the impression that he's lost, Floyd would di this at times and the commentary plus judges would give Manny those rounds due to sheer volume of attack aggression we know Spence doesn't have the defense that Floyd had, so Spence will get tagged.
These things should happen if Manny is trained correctly because he did this to Diaz, but if Manny's legs are totally gone and he's completely shot, he will try certain things but his quickness explosivness might be gone and he might not be able to pull the trigger, he will dance try counters get frustrated and explain he couldn't do the counters footwork anymore, if he has a little left in the tank, he will look good in spurts but fade late in the fight, but if he has one more fight left in him, he could pull out a close win, because he could beat Spence easily if he was still in his prime.