Only one game was decisive today, but it should have been two and it might have been all four. The day's one winner was Anish Giri, who won a nice game against Wang Hao on the white side of a Closed Catalan. Giri outplayed his opponent through the first 31 moves, and although he erred and let his opponent back into the game, Wang Hao repaid the favor with interest, and lost. That brought him within half a point of the leader, Ian Nepomniachtchi, and into a tie for second with Fabiano Caruana and Maxime Vachier-Lagrave.
The latter was a co-leader going into the previous round, but lost to Caruana to fall off the pace. He could have fallen even further back today, as he was completely lost against Ding Liren. Unfortunately for the latter, he passed over one easily winning move (36.Rxb6) en route to what he took to be a different winning idea (36.Rd1?! Qf6 37.d6??), only to discover (after 37...Re6!) that it wasn't winning at all. It was a pity, as his enterprising opening play, culminating in 15.Nd4!!, merited a better outcome.
At the top of the pile, Nepomniachtchi drew fairly comfortably, with Black, with Alexander Grischuk. But Grischuk gave him a serious opportunity at one moment with the interesting but dubious 26.Rxf7, sacrificing the exchange. (It worked for his opponent in the previous round, after all.) Had Nepo accepted the offer, he would have to find some accurate moves, but if he'd have managed he'd have enjoyed a meaningful advantage. Instead, he played it safe, declined the offer, and achieved the easy draw he would have had if Grischuk had played a normal 26th move.
Caruana may have also let an extra half a point slip through his fingers, and for the same reason: he rejected some free food. As in the Grischuk-Nepo game, it was a once-only opportunity, and also as in the Grischuk-Nepo game, it occurred on move 26. Had Caruana played 26...Nxa4, he may have finished the day tied for first. Even so, he remains in good shape with five rounds to go, and here are the pairings for round 10:
The round 9 games, with my annotations, are here.