He opened with a win on Monday, but lost another game.
Carlsen came out bad after losing three of the first six games of the tournament. That is why Monday's victory over strong Maxime Vachier-Lagrave is welcome.
The match against the French was decided by Carlsen in 34 moves. Vachier-Lagrave is ranked as the second best fast chess player in the world, behind Carlsen.
The first loss in nine years
In Monday's second game, Carlsen found himself in trouble against Sergei Karjakin, a player he had not lost to fast chess in nine years.
The party-evaluating computer showed all the way to Karjakin, and after 53 moves it was over. In addition to the win, the Russian also passed Carlsen in the tournament summary.
Magnus Carlsen has 7 points from 16 possible after eight games at St. Louis. Later on Monday, he will meet Shakhrijar Mamedjarov in the final party in a speed jacket.
Lost first place in the rankings
Poor tournament play in the US also means that Carlsen's leadership in a fast-paced chess accident is now much more scarce than it was before the weekend.
Vachier-Lagrave is just four points behind the Norwegians in the rankings after two games played on Monday night.
Tarshei J. Svensen A chess commentator writes on Twitter that Carlsen French could be captured during the tournament.
Armenian Levon Aronian won the tournament with 12 points, while Vachier-Lagrave finished second with 11 points.
Starting Tuesday, the St. Louis play lightning.