For the fourth time since 2012, Fabiano Caruana has defeated Magnus Carlsen. His win today with the black pieces was impressive, and his 3-0 score has him a point and a half clear of the field and two points ahead of Carlsen in the 2nd Sinquefield Cup. (It also has him at a very clear #2 on the Live Rating List, where he is now "only" 45 points behind the world champion.) All fantastic news for the young American-Italian, who really should scrap the second part of that hyphen.
Still, there are seven tough rounds to go, so it's too soon to crown him the winner of this week's strongest tournament ever. In the other games Maxime Vachier-Lagrave bounced back from yesterday's loss to beat Levon Aronian pretty handily. Aronian made some dubious decisions early in the game and missed a couple of nice ideas by his opponent, and went down in a hurry. They are now both at 50%.
In the last game to finish Veselin Topalov finally got on the scoreboard with a win over Hikaru Nakamura. Nakamura missed a winning opportunity early in the game and a second, later chance that could also have resulted in a win. In the end it was Topalov who took his opportunities in their very sharp game, and they are tied with Carlsen for 4th-6th (last) at 1-2.
Tomorrow's pairings: Vachier-Lagrave - Nakamura, Carlsen - Topalov, Caruana - Aronian
Update: A small addition: here are the games, with comments to Carlsen-Caruana.