When I want a detail of frequent punches, I also think about pacing. The more words between each jab, the slower the fight feels. I prefer these things reeling and done, so I’d render that sentence:
He pulled the fight tighter, landing a series of blows: cross-jaw, stomach, rib, uppercut. His opponent lost track of where the blows came from, couldn’t count them, as fleeting as grains of sand.
Each action having its own little sentence kills a fight. Second sentence implies that those 4 were just the start of the beat-down .