Both Murray and Karatsev have already played one match at the event and both score wins. Murray had a far easier job winning in two sets. Karatsev had a much tougher opponent and had to dig deeper in order to secure a spot in the next round.
The Russian hasn't had the best season so far, with a few decent performances but mostly playing at a level below his best overall. Murray has had a better year overall, including helping his country secure a spot in the Final 8 of the Davis Cup Finals recently.
When it comes to the H2H, we've only seen them play each other once before on the ATP Tour. Surprisingly, it was Karatsev who won that match, beating Murray 6-3 6-3 last year in Sydney. It came at a time when Murray wasn't playing on this level.
This one favours the Brit far more because the conditions will likely allow him to track down many balls, forcing Karatsev to overhit.
The Russian plays a rather simple style of play that consists of very flat shots that can be incredibly hard to counter in fast conditions. Zhuhai doesn't play as quick, with many describing it as one of the slowest courts on Tour.
That bodes well for Murray, who doesn't move as well as he used to but still can do enough to track down most balls. His defence will be crucial against Karatsev because the Russian will look to finish off rallies quickly, and if he can force him to commit mistakes, then he'll be closer to winning.
Of course, Karatsev won't miss all the time, so Murray will need to bring some shot-making to the rallies; otherwise, he risks playing Karatsev into a good rhythm. That happened to Matteo Arnaldi in the previous round, and the Italian paid the price for it.
Prediction: Andy Murray to win in three sets.